Small vessel and cooling system of engine for vessel

Abstract

To provide a small vessel capable of preventing cooling water from being accumulated in a flow path portion provided in a cylinder block during stop of an engine.SOLUTION: In a small vessel 100, a cooling flow path 50 is configured so that cooling water flows into a cylinder block 23 from the below through a lower end flow path port 23d arranged near a lower end of a flow path portion 23a provided in the cylinder block 23.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a cooling system for small ships and ship engines.

Background Art

[0002] Conventionally, a small ship equipped with a cooling flow path through which cooling water for cooling an engine flows is known (see, for example, Patent Document 1).

[0003] Patent Document 1 describes a small ship equipped with a cooling flow path through which cooling water for cooling an engine including a cylinder block and the like flows.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, although not described in Patent Document 1, in the small ship described in Patent Document 1, when the engine stops and cooling water stays in the flow path portion provided in the cylinder block, rust may occur on the cylinder block, or the cooling water may freeze when the small ship is used in a cold environment. Note that Patent Document 1 does not particularly describe a structure for suppressing the retention of cooling water in the flow path portion provided in the cylinder block when the engine stops. For this reason, a configuration capable of suppressing the retention of cooling water in the flow path portion provided in the cylinder block when the engine stops is desired.

[0006] The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a cooling system for a small ship and a marine engine that can suppress the retention of cooling water in a flow path portion provided in a cylinder block when the engine stops.

Means for Solving the Problems

[0007] To achieve the above object, a small ship according to a first aspect of the present invention includes a hull, an engine provided in the hull and including an exhaust manifold, a cylinder head, and a cylinder block, and a cooling flow path through which cooling water for cooling the engine flows. The cooling flow path is configured such that the cooling water that has flowed through the exhaust manifold flows into the cylinder block via the cylinder head. Near the outlet of the cooling water in the cylinder block, a thermostat is provided that adjusts the flow rate of the cooling water discharged from the cylinder block based on the temperature of the cooling water. The cooling flow path is configured such that the cooling water flows into the cylinder block from the lower side via a lower end flow path opening disposed near the lower end of the flow path portion provided in the cylinder block.

[0008] In the small ship according to the first aspect of the present invention, as described above, the cooling flow path is configured such that the cooling water flows into the cylinder block from the lower side via the lower end flow path opening disposed near the lower end of the flow path portion provided in the cylinder block. As a result, the flow path connected to the cylinder block via the lower end flow path opening extends downward, so that drainage can be performed from the flow path portion provided in the cylinder block to the lower end flow path opening when the engine stops. As a result, it is possible to suppress the retention of cooling water in the flow path portion provided in the cylinder block when the engine stops.

[0009] Also, in the small ship according to the first aspect, as described above, the cooling flow path is configured such that the cooling water flowing through the exhaust manifold flows into the cylinder block via the cylinder head, and near the outlet of the cooling water in the cylinder block, a thermostat is provided for adjusting the flow rate of the cooling water discharged from the cylinder block based on the temperature of the cooling water. As a result, since the cooling water flowing into the cylinder block passes through the cylinder head, it is possible to prevent the cooling water flowing into the cylinder block from becoming excessively low in temperature. Further, the thermostat can adjust the temperature of the cooling water flowing through the flow path portion provided in the cylinder block to an appropriate temperature. As a result of these, excessive cooling of the cylinder block can be suppressed.

[0010] In the small ship according to the first aspect, preferably, the engine includes an oil cooler, and the cooling flow path is configured such that the cooling water flowing through the oil cooler flows into the cylinder block from below via the lower end flow port. With this configuration, the flow path for allowing the cooling water that has cooled the oil cooler to flow into the cylinder block can be used as the flow path for draining water from the flow path portion provided in the cylinder block via the lower end flow port when the engine is stopped. As a result, the configuration of the cooling flow path can be simplified compared to the case where a dedicated flow path for draining water is provided.

[0011] In the small ship according to the first aspect, preferably, in the cooling flow path, the cooling water that has passed through the cylinder head is discharged to the outside of the cylinder head through an upper end flow port disposed near the upper end of the flow path portion provided in the cylinder head. With this configuration, since the upper end flow port is disposed near the upper end of the flow path portion provided in the cylinder head, air mixed in the cooling water can be included in the cooling water discharged from the flow path portion provided in the cylinder head through the upper end flow port. That is, air can be removed from the cooling water flowing through the flow path portion provided in the cylinder head through the upper end flow port. As a result, it is possible to suppress a decrease in the cooling performance of the cooling water flowing through the cooling flow path due to air being mixed in the cooling water.

[0012] In the configuration in which the cooling water that has passed through the cylinder head is discharged to the outside of the cylinder head through the upper end flow port, preferably, a rectifier / regulator used for engine control is further provided, and the cooling flow path is configured such that the cooling water discharged to the outside of the cylinder head through the upper end flow port is discharged to the outside of the hull via the rectifier / regulator. With this configuration, the flow path for removing air from the cooling water flowing through the flow path portion provided in the cylinder head through the upper end flow port can be used as the flow path for allowing the cooling water discharged from the flow path portion provided in the cylinder head to flow into the rectifier / regulator to cool the rectifier / regulator. As a result, the configuration of the cooling flow path can be simplified as compared with the case where a dedicated flow path for air removal is provided.

[0013] In a configuration where the cooling water flowing through the cylinder head is discharged to the outside of the cylinder head through the upper end flow port, preferably, the cooling flow path is configured such that a part of the cooling water flowing through the cylinder head flows into the cylinder block, and the remaining part of the cooling water flowing through the cylinder head is discharged to the outside of the cylinder head through the upper end flow port. By configuring in this way, it is possible to suppress an excessive increase in the flow path of the cooling water discharged from the cylinder head, so that the configuration of the cooling flow path can be simplified.

[0014] In the small ship according to the first aspect, preferably, the cooling flow path is configured such that the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block is smaller than the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head. By configuring in this way, since the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block becomes relatively small, it is possible to suppress an excessive increase in the flow rate of the cooling water flowing from the flow path portion provided in the cylinder head into the flow path portion provided in the cylinder block. As a result, a configuration for suppressing excessive cooling of the cylinder block can be easily realized.

[0015] In a configuration where the cooling water flowing through the cylinder head is discharged to the outside of the cylinder head through the upper end flow port, preferably, the cooling flow path is configured such that the cross-sectional area of the flow path connected to the cylinder head through the upper end flow port is smaller than the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head. By configuring in this way, since the cross-sectional area of the flow path connected to the cylinder head through the upper end flow port becomes relatively small, it is possible to suppress an excessive increase in the flow rate of the cooling water discharged from the cylinder head through the upper end flow port. As a result, it is possible to suppress a situation where the flow rate of the cooling water flowing from the flow path portion provided in the cylinder head into the flow path portion provided in the cylinder block becomes excessively small and the cylinder block cannot be properly cooled.

[0016] In the small ship according to the first aspect, preferably, the cooling flow path is configured such that the cross-sectional area of the flow path connected to the cylinder head via the upper end flow port is smaller than the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block. With this configuration, it is possible to suppress the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block from becoming excessively small. As a result, it is possible to suppress the flow rate of the cooling water flowing from the flow path portion provided in the cylinder head to the flow path portion provided in the cylinder block from becoming excessively small and prevent the cylinder block from being inadequately cooled.

[0017] In the small ship according to the first aspect, preferably, the cooling flow path is configured such that the cross-sectional area of the flow path connected to the cylinder block via the lower end flow port is smaller than the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block. With this configuration, it is possible to suppress the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block from becoming excessively small. As a result, it is possible to suppress the flow rate of the cooling water flowing from the flow path portion provided in the cylinder head to the flow path portion provided in the cylinder block from becoming excessively small and prevent the cylinder block from being inadequately cooled.

[0018] In the configuration in which the cooling water that has flowed through the oil cooler flows into the cylinder block from below via the lower end flow port, preferably, the cooling flow path is configured such that a part of the cooling water flowing in from the outside of the hull flows into the exhaust manifold, and the remaining part of the cooling water flowing in from the outside of the hull flows into the oil cooler. With this configuration, a part of the cooling water flowing in from the outside of the hull flows into the exhaust manifold, another part of the cooling water flowing in from the outside of the hull flows into the oil cooler, and the remaining part of the cooling water flowing in from the outside of the hull flows into the parts constituting the small ship other than the exhaust manifold and the oil cooler. Compared with the case where the flow rate of the cooling water flowing into the exhaust manifold becomes excessively small, it is possible to suppress the flow rate of the cooling water flowing into the exhaust manifold from becoming excessively small, so that the exhaust manifold, which becomes relatively hot, can be sufficiently cooled.

[0019] In the small ship according to the first aspect, preferably, the thermostat is configured to adjust the flow rate of the cooling water discharged from the cylinder block so that the temperature of the cooling water becomes a predetermined temperature of approximately 50 degrees or more and approximately 70 degrees or less. With this configuration, it is possible to easily adjust the cooling water flowing through the flow path portion provided in the cylinder block to an appropriate temperature. As a result, a configuration for suppressing excessive cooling of the cylinder block can be easily realized.

[0020] In the small ship according to the first aspect, preferably, the cooling flow path is configured such that all of the cooling water that has passed through the exhaust manifold flows into the cylinder head. With this configuration, the flow rate of the cooling water flowing into the cylinder head can be made relatively large, so that the cylinder head, which becomes relatively hot, can be sufficiently cooled.

[0021] In the small ship according to the first aspect, preferably, it further includes a jet propulsion unit that generates thrust by the driving force of the engine. With this configuration, in a jet propulsion type small ship, it is possible to suppress excessive cooling of the cylinder block and to suppress the cooling water from staying in the flow path portion provided in the cylinder block when the engine stops.

[0022] Further, in order to achieve the above object, a cooling system for a marine engine according to a second aspect of the present invention is provided on a hull and is configured such that cooling water for cooling an engine including an exhaust manifold, a cylinder head, and a cylinder block flows therethrough. The cooling flow path includes a cooling flow path through which the cooling water that has passed through the exhaust manifold flows into the cylinder block via the cylinder head, and a thermostat provided near the outlet of the cooling water of the cylinder block and configured to adjust the flow rate of the cooling water discharged from the cylinder block based on the temperature of the cooling water. The cooling flow path is configured such that the cooling water flows into the cylinder block from the lower side through a lower end flow path opening disposed near the lower end of the flow path portion provided in the cylinder block.

[0023] In the cooling system of the marine engine according to the second aspect of the present invention, as described above, the cooling flow path is configured such that cooling water flows into the cylinder block from the lower side through a lower end flow path opening disposed near the lower end of the flow path portion provided in the cylinder block. Thereby, similar to the small ship according to the first aspect, it is possible to suppress the cooling water from staying in the flow path portion provided in the cylinder block when the engine stops.

[0024] Also, in the cooling system of the marine engine according to the second aspect, as described above, the cooling flow path is configured such that the cooling water that has passed through the exhaust manifold flows into the cylinder block via the cylinder head, and near the outlet of the cooling water in the cylinder block, a thermostat is provided for adjusting the flow rate of the cooling water discharged from the cylinder block based on the temperature of the cooling water. Thereby, similar to the small ship according to the first aspect, it is possible to suppress excessive cooling of the cylinder block.

[0025] In the cooling system of the marine engine according to the second aspect, preferably, the engine includes an oil cooler, and the cooling flow path is configured such that the cooling water that has passed through the oil cooler flows into the cylinder block from the lower side through the lower end flow path opening. With this configuration, similar to the small ship according to the first aspect, the configuration of the cooling flow path can be simplified as compared with the case where a dedicated flow path for draining water is provided.

[0026] In the cooling system of the marine engine according to the second aspect, preferably, the cooling flow path is configured such that the cooling water that has passed through the cylinder head is discharged to the outside of the cylinder head through an upper end flow path opening disposed near the upper end of the flow path portion provided in the cylinder head. With this configuration, similar to the small ship according to the first aspect, it is possible to suppress a decrease in the cooling performance of the cooling water flowing through the cooling flow path due to air being mixed into the cooling water.

[0027] In the configuration of the cooling system for a marine engine according to the second aspect, where the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head through the upper end flow port, preferably, a rectifier / regulator used for controlling the engine is provided on the hull, and the cooling flow path is configured such that the cooling water discharged to the outside of the cylinder head through the upper end flow port is discharged to the outside of the hull via the rectifier / regulator. With this configuration, similar to the small ship according to the first aspect, the configuration of the cooling flow path can be simplified compared to the case where a dedicated flow path for air bleeding is provided.

[0028] In the configuration of the cooling system for a marine engine according to the second aspect, where the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head through the upper end flow port, preferably, the cooling flow path is configured such that a part of the cooling water that has flowed through the cylinder head flows into the cylinder block, and the remaining part of the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head through the upper end flow port. With this configuration, similar to the small ship according to the first aspect, the configuration of the cooling flow path can be simplified.

[0029] In the cooling system for a marine engine according to the second aspect, preferably, the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block in the cooling flow path is configured to be smaller than the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head. With this configuration, similar to the small ship according to the first aspect, a configuration for suppressing excessive cooling of the cylinder block can be easily realized.

[0030] In the configuration where the cooling water that has flowed through the cylinder head in the cooling system of the marine engine according to the second aspect is discharged to the outside of the cylinder head through the upper end flow port, preferably, the cooling flow path is configured such that the cross-sectional area of the flow path connected to the cylinder head through the upper end flow port is smaller than the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head. With this configuration, similar to the small ship according to the first aspect, it is possible to suppress the failure to properly cool the cylinder block.

Effect of the Invention

[0031] According to the present invention, as described above, it is possible to provide a cooling system for a small ship and a marine engine that can suppress the retention of cooling water in the flow path portion provided in the cylinder block when the engine stops.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Mode for Carrying Out the Invention

[0033] Hereinafter, embodiments embodying the present invention will be described with reference to the drawings.

[0034] With reference to FIGS. 1 to 10, a small ship 100 and a cooling system 110 for a marine engine according to an embodiment of the present invention will be described.

[0035] (Overall Configuration of Small Ship) As shown in FIG. 1, the small ship 100 is a water jet propulsion boat (water motorcycle). That is, the small ship 100 is a personal watercraft. The small ship 100 includes a hull 10, an engine 20 provided inside the hull 10, and a jet propulsion type propulsion unit 30 that generates thrust by the driving force of the engine 20. Note that FWD and BWD in FIG. 1 indicate the front and rear of the small ship 100, respectively.

[0036] The engine 20 includes a crankshaft 21, and the engine 20 is configured to obtain a driving force for rotating the crankshaft 21 by burning a mixture of air and fuel sucked through an intake passage (not shown) provided with a throttle valve (not shown) in a combustion chamber.

[0037] The propulsion unit 30 is configured to take in water from a water channel 31 having an opening provided on the lower surface at the rear of the small ship 100 by being driven by the engine 20, and to inject the taken-in water from a nozzle 32 located at the rear end of the small ship 100. As a result, the small ship 100 is propelled.

[0038] The propulsion unit 30 includes a drive shaft 33, an impeller 34, a nozzle 32, a deflector 35, and a reverse gate (bucket) 36.

[0039] The drive shaft 33 extends in the front-rear direction, the front end is connected to the crankshaft 21, and the rear end is disposed in the water channel 31. An impeller 34 is fixed near the rear end of the drive shaft 33.

[0040] The impeller 34 is configured to generate a flow toward the nozzle 32 in the water channel 31 by rotating together with the drive shaft 33.

[0041] The nozzle 32 is disposed at the most downstream position of the water channel 31 where the impeller 34 is disposed. The nozzle 32 has a function as a water discharge port (injection port). That is, the nozzle 32 is configured to inject water to generate a propulsion force. A deflector 35 and a reverse gate 36 are installed on the nozzle 32.

[0042] The deflector 35 is configured to be rotatable in the left-right direction about an axis extending in the up-down direction. That is, the deflector 35 is configured to be able to change the direction of the water injected from the nozzle 32 in the left-right direction.

[0043] The reverse gate 36 is configured to be rotatable in the up-down direction about an axis extending in the left-right direction. That is, the reverse gate 36 is configured to be able to change the direction of the water injected from the nozzle 32 in the front-rear direction.

[0044] (Configuration of the engine) As shown in FIG. 2, the engine 20 includes a cylinder head 22, a cylinder block 23, an exhaust manifold 24, and an exhaust pipe 25. The cylinder block 23 is disposed below the cylinder head 22. The exhaust passage in the exhaust manifold 24 is connected to the internal space of the cylinder head 22, and the exhaust gas discharged from the cylinder head 22 flows therethrough. The exhaust passage in the exhaust pipe 25 is connected to the exhaust passage in the exhaust manifold 24, and the exhaust gas that has flowed through the exhaust passage in the exhaust manifold 24 flows into it.

[0045] The engine 20 includes an oil cooler 27. The oil cooler 27 is configured to cool the circulating oil used in the engine 20.

[0046] The small ship 100 includes a rectifier / regulator 41. The rectifier / regulator 41 is used for controlling the engine 20.

[0047] The engine 20 includes a lid member 26. As shown in FIG. 3, the lid member 26 is attached to the upper part of the cylinder head 22. The lid member 26 is formed by combining a first housing part 26a having an X shape in plan view and a second housing part 26b having an annular polygonal shape (hexagonal shape) with each other. In plan view, the central position of the X-shaped first housing part 26a and the central position of the annular polygonal-shaped second housing part 26b are substantially coincident. The X-shaped first housing part 26a protrudes upward from the annular polygonal-shaped second housing part 26b. Therefore, the annular polygonal-shaped second housing part 26b is divided into a plurality (four) by the X-shaped first housing part 26a in plan view. A plurality (four) of gaps 26c (through holes) are provided inside the annular polygonal-shaped second housing part 26b and between the X-shaped first housing part 26a and the annular polygonal-shaped second housing part 26b.

[0048] The first housing part 26a and the second housing part 26b are formed of, for example, a plant-derived cellulose nanofiber (CNF)-reinforced resin. The plant-derived cellulose nanofiber-reinforced resin is a high-strength material produced by kneading and dispersing plant-derived cellulose nanofibers, which are biomass materials utilizing wood resources, into a resin such as polypropylene. Note that the first housing part 26a and the second housing part 26b may be formed of other materials. Also, the first housing part 26a and the second housing part 26b may be formed of different materials from each other.

[0049] (Configuration of the cooling flow path) As shown in FIG. 4, the small ship 100 includes a cooling flow path 50 through which cooling water for cooling the engine 20 (see FIG. 2) flows. That is, the small ship 100 is provided with a cooling system 110 for a marine engine including the cooling flow path 50.

[0050] The cooling flow path 50 is configured such that water (such as seawater or fresh water) outside the hull 10 is supplied as cooling water into the cooling flow path 50 by a jet pump 51. The jet pump 51 is provided between the impeller 34 (see FIG. 1) and the nozzle 32 (see FIG. 1).

[0051] The cooling flow path 50 is configured such that a part of the cooling water flowing in from outside the hull 10 flows into the exhaust manifold 24, and the remaining part of the cooling water flowing in from outside the hull 10 flows into the oil cooler 27. Specifically, a joint 52 that branches a flow path toward the exhaust manifold 24 and a flow path toward the oil cooler 27 is provided on the downstream side of the jet pump 51.

[0052] The small ship 100 (the cooling system 110 for a marine engine) includes a water washing device 53. The water washing device 53 includes an adapter to which a water supply hose can be attached. When washing the cooling flow path 50, a water supply hose is attached to the adapter of the water washing device 53.

[0053] The cooling flow path 50 is configured such that all of the cooling water that has flowed through the exhaust manifold 24 flows into the cylinder head 22. Specifically, the cooling flow path 50 is configured such that all of the cooling water that has flowed through the flow path portion 24a provided in the exhaust manifold 24 flows into the flow path portion 22a provided in the cylinder head 22 without passing through other portions of the small ship 100 to be cooled. As shown in FIG. 5, the flow path portion 24a provided in the exhaust manifold 24 (see FIG. 4) is a flow path formed in a water jacket 24b disposed so as to surround the exhaust flow path of the exhaust manifold 24. Further, the flow path portion 22a provided in the cylinder head 22 (see FIG. 4) is a flow path formed in a water jacket 22b disposed so as to surround the space constituting the combustion chamber of the cylinder head 22.

[0054] As shown in FIG. 4, the cooling flow path 50 is configured such that the cooling water that has flowed through the exhaust manifold 24 flows into the cylinder block 23 via the cylinder head 22. Specifically, the cooling flow path 50 is configured such that all of the cooling water that has flowed through the flow path portion 24a provided in the exhaust manifold 24 flows into the flow path portion 22a provided in the cylinder head 22, and then a part of the cooling water that has flowed into the cylinder head 22 flows into the flow path portion 23a provided in the cylinder block 23. As shown in FIG. 5, the flow path portion 23a provided in the cylinder block 23 (see FIG. 4) is a flow path formed in a water jacket 23b disposed so as to surround the space where the piston etc. of the cylinder block 23 is provided.

[0055] As shown in FIG. 4, in the small ship 100 (the cooling system 110 for the marine engine), a thermostat 54 is provided downstream of the cylinder block 23 to adjust the flow rate of the cooling water discharged from the cylinder block 23 based on the temperature of the cooling water. As shown in FIG. 5, the thermostat 54 is provided near the outlet 23c of the cooling water of the cylinder block 23. Specifically, the thermostat 54 is attached to the outlet 23c of the cooling water in the flow path portion 23a provided in the cylinder block 23. The thermostat 54 is configured to adjust the flow rate of the cooling water discharged from the cylinder block 23 so that the temperature of the cooling water becomes a predetermined temperature of approximately 50 degrees or more and approximately 70 degrees or less.

[0056] As shown in FIG. 4, the cooling water discharged from the cylinder block 23 is configured to be discharged to the outside of the hull 10 after passing through the thermostat 54.

[0057] As shown in FIGS. 6 and 7, the cooling flow path 50 is configured such that the cooling water flows into the cylinder block 23 (see FIG. 4) from the lower side through the lower end flow path opening 23d disposed near the lower end of the flow path portion 23a provided in the cylinder block 23. Also, the cooling flow path 50 is configured such that the cooling water that has passed through the oil cooler 27 flows into the cylinder block 23 from the lower side through the lower end flow path opening 23d. Specifically, the cooling flow path 50 is configured such that a part of the cooling water that has passed through the flow path portion 27a provided in the oil cooler 27 flows into the flow path portion 23a provided in the cylinder block 23 from the lower side through the lower end flow path opening 23d. As shown in FIG. 4, the remaining part of the cooling water that has passed through the flow path portion 27a provided in the oil cooler 27 in the cooling flow path 50 is configured to be discharged to the outside of the hull 10.

[0058] As shown in FIGS. 5 and 8, the cooling flow path 50 is configured such that the cooling water flowing through the cylinder head 22 is discharged to the outside of the cylinder head 22 through an upper end flow port 22c disposed near the upper end of a flow path portion 22a provided in the cylinder head 22. Specifically, the cooling flow path 50 is configured such that a part of the cooling water flowing through the cylinder head 22 flows into the cylinder block 23, and the remaining part of the cooling water flowing through the flow path portion 22a provided in the cylinder head 22 is discharged to the outside of the flow path portion 22a provided in the cylinder head 22 through the upper end flow port 22c. Further, the cooling flow path 50 is configured such that the cooling water discharged to the outside of the flow path portion 22a provided in the cylinder head 22 through the upper end flow port 22c is discharged to the outside of the hull 10 via a flow path portion 41a provided in the rectifier / regulator 41. That is, as shown in FIG. 4, the cooling water flowing through the cylinder head 22 is configured to be discharged to the outside of the hull 10 after passing through the thermostat 54, or to be discharged to the outside of the hull 10 after passing through the rectifier / regulator 41.

[0059] The cooling flow path 50 is configured such that the cooling water discharged to the outside of the cylinder head 22 through the upper end flow port 22c passes through the exhaust pipe 25 and the water lock 55 in this order via the rectifier / regulator 41 and is then discharged to the outside of the hull 10. The cooling flow path 50 is configured such that the cooling water flowing into the exhaust pipe 25 is mixed with the exhaust gas flowing in from the exhaust flow path in the exhaust manifold 24. And the water lock 55 is configured to store the cooling water mixed with the exhaust gas. The mixture of the exhaust gas and the cooling water stored in the water lock 55 is configured to be discharged to the outside of the hull 10 by the pressure of the exhaust gas.

[0060] (Cross-sectional area of the flow path in each part of the cooling flow path) As shown in FIG. 10, the cooling flow path 50 (see FIG. 4) is configured such that the cross-sectional area S1 of the flow path F1 connecting between the cylinder head 22 (see FIG. 4) and the cylinder block 23 (see FIG. 4) is smaller than the cross-sectional area S2 of the flow path F2 connecting between the exhaust manifold 24 (see FIG. 4) and the cylinder head 22. As shown in FIG. 9, the flow path F1 connecting between the cylinder head 22 and the cylinder block 23 is a plurality of holes formed in a head gasket 56 disposed between the cylinder head 22 and the cylinder block 23. The plurality of holes are arranged so as to surround each of the plurality of through holes 56a through which the piston passes. As shown in FIG. 5, the flow path F2 connecting between the exhaust manifold 24 and the cylinder head 22 is composed of a plurality of pipes.

[0061] As shown in FIG. 10, the cooling flow path 50 (see FIG. 4) is configured such that the cross-sectional area S3 of the flow path F3 connecting between the cylinder head 22 (see FIG. 4) and the rectifier / regulator 41 (see FIG. 4) is smaller than the cross-sectional area S2 of the flow path F2 connecting between the exhaust manifold 24 (see FIG. 4) and the cylinder head 22. As shown in FIG. 5, the flow path F3 connecting between the cylinder head 22 and the rectifier / regulator 41 is composed of one pipe. Note that the flow path F3 connecting between the cylinder head 22 and the rectifier / regulator 41 is an example of the "flow path connected to the cylinder head via the upper end flow port" in the claims.

[0062] As shown in FIG. 10, the cooling flow path 50 is configured such that the cross-sectional area S3 of the flow path F3 connecting between the cylinder head 22 and the rectifier / regulator 41 is smaller than the cross-sectional area S1 of the flow path F1 connecting between the cylinder head 22 and the cylinder block 23.

[0063] The cooling flow path 50 is configured such that the cross-sectional area S4 of the flow path F4 connecting between the oil cooler 27 and the cylinder block 23 is smaller than the cross-sectional area S1 of the flow path F1 connecting between the cylinder head 22 and the cylinder block 23. In FIG. 10, the cross-sectional line S3 and the cross-sectional area S4 are shown to be of the same size, but they may be different from each other. As shown in FIG. 6, the flow path F4 connecting between the oil cooler 27 and the cylinder block 23 is composed of one pipe. The flow path F4 connecting between the oil cooler 27 and the cylinder block 23 is an example of the "flow path connected to the cylinder block via the lower end flow path opening" in the claims.

[0064] [Effects of the Embodiment] In this embodiment, the following effects can be obtained.

[0065] In this embodiment, as described above, the cooling flow path 50 is configured such that cooling water flows into the cylinder block 23 from the lower side through the lower end flow path opening 23d disposed near the lower end of the flow path portion 23a provided in the cylinder block 23. Thereby, since the flow path connected to the cylinder block 23 via the lower end flow path opening 23d extends downward, draining can be performed from the flow path portion 23a provided in the cylinder block 23 through the lower end flow path opening 23d when the engine 20 stops. As a result, it is possible to suppress the cooling water from remaining in the flow path portion 23a provided in the cylinder block 23 when the engine 20 stops.

[0066] Also, in the present embodiment, the cooling channel 50 is configured such that the cooling water that has flowed through the exhaust manifold 24 flows into the cylinder block 23 via the cylinder head 22. Further, near the outlet 23c of the cooling water in the cylinder block 23, a thermostat 54 is provided that adjusts the flow rate of the cooling water discharged from the cylinder block 23 based on the temperature of the cooling water. As a result, since the cooling water flowing into the cylinder block 23 passes through the cylinder head 22, it is possible to suppress the cooling water flowing into the cylinder block 23 from becoming excessively low in temperature. Also, the thermostat 54 can adjust the temperature of the cooling water flowing through the flow path portion 23a provided in the cylinder block 23 to an appropriate temperature. As a result of these, excessive cooling of the cylinder block 23 can be suppressed.

[0067] Also, in the present embodiment, as described above, the engine 20 includes an oil cooler 27. And the cooling channel 50 is configured such that the cooling water that has flowed through the oil cooler 27 flows into the cylinder block 23 from below via the lower end flow port 23d. As a result, the channel for allowing the cooling water that has cooled the oil cooler 27 to flow into the cylinder block 23 can be used as a channel for draining water from the flow path portion 23a provided in the cylinder block 23 via the lower end flow port 23d when the engine 20 is stopped. As a result, the configuration of the cooling channel 50 can be simplified as compared with the case where a dedicated channel for draining water is provided.

[0068] Also, in the present embodiment, as described above, the cooling channel 50 is configured such that the cooling water that has flowed through the cylinder head 22 is discharged to the outside of the cylinder head 22 through the upper end flow port 22c disposed near the upper end of the flow path portion 22a provided in the cylinder head 22. As a result, since the upper end flow port 22c is disposed near the upper end of the flow path portion 22a provided in the cylinder head 22, air mixed in the cooling water can be included in the cooling water discharged from the flow path portion 22a provided in the cylinder head 22 through the upper end flow port 22c. That is, air can be removed from the cooling water flowing through the flow path portion 22a provided in the cylinder head 22 through the upper end flow port 22c. As a result, it is possible to suppress a decrease in the cooling performance of the cooling water flowing through the cooling channel 50 due to air being mixed in the cooling water.

[0069] Also, in the present embodiment, as described above, the small ship 100 includes a rectifier / regulator 41 used for controlling the engine 20. And the cooling channel 50 is configured such that the cooling water discharged to the outside of the cylinder head 22 through the upper end flow port 22c is discharged to the outside of the hull 10 via the rectifier / regulator 41. As a result, the flow path for removing air from the cooling water flowing through the flow path portion 22a provided in the cylinder head 22 through the upper end flow port 22c can be used as the flow path for flowing the cooling water discharged from the flow path portion 22a provided in the cylinder head 22 into the rectifier / regulator 41 to cool the rectifier / regulator 41. As a result, the configuration of the cooling channel 50 can be simplified as compared with the case where a dedicated flow path for removing air is provided.

[0070] Further, in the present embodiment, as described above, in the cooling channel 50, part of the cooling water that has flowed through the cylinder head 22 flows into the cylinder block 23, and the remaining part of the cooling water that has flowed through the cylinder head 22 is discharged to the outside of the cylinder head 22 through the upper end flow port 22c. Thereby, it is possible to suppress an excessive increase in the flow path of the cooling water discharged from the cylinder head 22, so that the configuration of the cooling channel 50 can be simplified.

[0071] Further, in the present embodiment, as described above, in the cooling channel 50, the cross-sectional area S1 of the flow path F1 connecting between the cylinder head 22 and the cylinder block 23 is configured to be smaller than the cross-sectional area S2 of the flow path F2 connecting between the exhaust manifold 24 and the cylinder head 22. Thereby, since the cross-sectional area S1 of the flow path F1 connecting between the cylinder head 22 and the cylinder block 23 becomes relatively small, it is possible to suppress an excessive increase in the flow rate of the cooling water flowing from the flow path portion 22a provided in the cylinder head 22 into the flow path portion 23a provided in the cylinder block 23. As a result, a configuration for suppressing excessive cooling of the cylinder block 23 can be easily realized.

[0072] Further, in the present embodiment, as described above, in the cooling channel 50, the cross-sectional area S3 of the flow path F3 connecting between the cylinder head 22 and the rectifier / regulator 41 (the flow path connected to the cylinder head 22 through the upper end flow port) is configured to be smaller than the cross-sectional area S2 of the flow path F2 connecting between the exhaust manifold 24 and the cylinder head 22. Thereby, since the cross-sectional area S3 of the flow path F3 connecting between the cylinder head 22 and the rectifier / regulator 41 becomes relatively small, it is possible to suppress an excessive increase in the flow rate of the cooling water discharged from the cylinder head 22 through the upper end flow port 22c. As a result, it is possible to suppress a situation where the flow rate of the cooling water flowing from the flow path portion 22a provided in the cylinder head 22 into the flow path portion 23a provided in the cylinder block 23 becomes excessively small and the cylinder block 23 cannot be properly cooled.

[0073] Also, in the present embodiment, as described above, the cooling channel 50 is configured such that the cross-sectional area S3 of the channel F3 (the channel connected to the cylinder head via the upper end channel opening) connecting between the cylinder head 22 and the rectifier / regulator 41 is smaller than the cross-sectional area S1 of the channel F1 connecting between the cylinder head 22 and the cylinder block 23. Thereby, it is possible to suppress the cross-sectional area S1 of the channel F1 connecting between the cylinder head 22 and the cylinder block 23 from becoming excessively small. As a result, it is possible to suppress the flow rate of the cooling water flowing from the channel portion 22a provided in the cylinder head 22 to the channel portion 23a provided in the cylinder block 23 from becoming excessively small and prevent the proper cooling of the cylinder block 23 from becoming impossible.

[0074] Also, in the present embodiment, as described above, the cooling channel 50 is configured such that the cross-sectional area S4 of the channel F4 (the channel connected to the cylinder block via the lower end channel opening) connecting between the oil cooler 27 and the cylinder block 23 is smaller than the cross-sectional area S1 of the channel F1 connecting between the cylinder head 22 and the cylinder block 23. Thereby, it is possible to suppress the cross-sectional area S1 of the channel F1 connecting between the cylinder head 22 and the cylinder block 23 from becoming excessively small. As a result, it is possible to suppress the flow rate of the cooling water flowing from the channel portion 22a provided in the cylinder head 22 to the channel portion 23a provided in the cylinder block 23 from becoming excessively small and prevent the proper cooling of the cylinder block 23 from becoming impossible.

[0075] Further, in the present embodiment, as described above, the cooling flow path 50 is configured such that a part of the cooling water flowing in from the outside of the hull 10 flows into the exhaust manifold 24, and the remaining part of the cooling water flowing in from the outside of the hull 10 flows into the oil cooler 27. Thereby, a part of the cooling water flowing in from the outside of the hull 10 flows into the exhaust manifold 24, another part of the cooling water flowing in from the outside of the hull 10 flows into the oil cooler 27, and the remaining part of the cooling water flowing in from the outside of the hull 10 flows into the parts constituting the small ship 100 other than the exhaust manifold 24 and the oil cooler 27. Compared with the case, it is possible to suppress an excessive decrease in the flow rate of the cooling water flowing into the exhaust manifold 24, so that the exhaust manifold 24, which becomes relatively high in temperature, can be sufficiently cooled.

[0076] Further, in the present embodiment, as described above, the thermostat 54 is configured to adjust the flow rate of the cooling water discharged from the cylinder block 23 so that the temperature of the cooling water becomes a predetermined temperature of approximately 50 degrees or more and approximately 70 degrees or less. Thereby, the cooling water flowing through the flow path portion 23a provided in the cylinder block 23 can be easily adjusted to an appropriate temperature. As a result, a configuration for suppressing excessive cooling of the cylinder block 23 can be easily realized.

[0077] Further, in the present embodiment, as described above, the cooling flow path 50 is configured such that all of the cooling water that has flowed through the exhaust manifold 24 flows into the cylinder head 22. Thereby, the flow rate of the cooling water flowing into the cylinder head 22 can be made relatively large, so that the cylinder head 22, which becomes relatively high in temperature, can be sufficiently cooled.

[0078] Further, in the present embodiment, as described above, the small ship 100 includes a jet propulsion unit 30 that generates thrust by the driving force of the engine 20. Thereby, in the jet propulsion type small ship 100, it is possible to prevent excessive suppression of the cylinder block 23 and to suppress the cooling water from staying in the flow path portion 23a provided in the cylinder block 23 when the engine 20 stops.

[0079] [Modification Example] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is indicated by the scope of claims rather than the description of the above embodiments, and further includes all changes (modification examples) within the meaning and scope equivalent to the scope of claims.

[0080] For example, in the above embodiment, an example is shown in which the small ship 100 includes a jet propulsion unit 30 that generates thrust by the driving force of the engine 20, but the present invention is not limited thereto. In the present invention, the small ship may include a propulsion unit other than the jet propulsion type.

[0081] Also, in the above embodiment, an example is shown in which the cooling flow path 50 is configured such that all of the cooling water flowing through the exhaust manifold 24 flows into the cylinder head 22, but the present invention is not limited thereto. In the present invention, the cooling flow path may be configured such that only a part of the cooling water flowing through the exhaust manifold flows into the cylinder head.

[0082] Also, in the above embodiment, an example is shown in which the thermostat 54 is configured to adjust the flow rate of the cooling water discharged from the cylinder block 23 so that the temperature of the cooling water becomes a predetermined temperature of approximately 50 degrees or more and approximately 70 degrees or less, but the present invention is not limited thereto. In the present invention, the thermostat may be configured to adjust the flow rate of the cooling water discharged from the cylinder block so that the temperature of the cooling water becomes a predetermined temperature of less than approximately 50 degrees or greater than approximately 70 degrees.

[0083] In the above-described embodiment, an example is shown in which the cooling channel 50 is configured such that a part of the cooling water flowing in from the outside of the hull 10 flows into the exhaust manifold 24, and the remaining part of the cooling water flowing in from the outside of the hull 10 flows into the oil cooler 27. However, the present invention is not limited to this. In the present invention, the cooling channel may be configured such that a part of the cooling water flowing in from the outside of the hull flows into the exhaust manifold, another part of the cooling water flowing in from the outside of the hull flows into the oil cooler, and the remaining part of the cooling water flowing in from the outside of the hull flows into a part constituting a small ship other than the exhaust manifold and the oil cooler.

[0084] In the above-described embodiment, an example is shown in which the cooling channel 50 is configured such that the cross-sectional area S4 of the channel F4 (the channel connected to the cylinder block via the lower end flow port) connecting between the oil cooler 27 and the cylinder block 23 is smaller than the cross-sectional area S1 of the channel F1 connecting between the cylinder head 22 and the cylinder block 23. However, the present invention is not limited to this. In the present invention, the cooling channel may be configured such that the cross-sectional area of the channel connected to the cylinder block via the lower end flow port is the same as or larger than the cross-sectional area of the channel connecting between the cylinder head and the cylinder block.

[0085] In the above-described embodiment, an example is shown in which the cooling channel 50 is configured such that the cross-sectional area S3 of the channel F3 (the channel connected to the cylinder head via the upper end flow port) connecting between the cylinder head 22 and the rectifier / regulator 41 is smaller than the cross-sectional area S1 of the channel F1 connecting between the cylinder head 22 and the cylinder block 23. However, the present invention is not limited to this. In the present invention, the cooling channel may be configured such that the cross-sectional area of the channel connected to the cylinder head via the upper end flow port is the same as or larger than the cross-sectional area of the channel connecting between the cylinder head and the cylinder block.

[0086] Further, in the above embodiment, an example is shown in which the cooling flow path 50 is configured such that the cross-sectional area S3 of the flow path F3 (the flow path connected to the cylinder head via the upper end flow path opening) connecting between the cylinder head 22 and the rectifier / regulator 41 is smaller than the cross-sectional area S2 of the flow path F2 connecting between the exhaust manifold 24 and the cylinder head 22. However, the present invention is not limited to this. In the present invention, the cooling flow path may be configured such that the cross-sectional area of the flow path connected to the cylinder head via the upper end flow path opening is the same as, or larger than, the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head.

[0087] Further, in the above embodiment, an example is shown in which the cooling flow path 50 is configured such that the cross-sectional area S1 of the flow path F1 connecting between the cylinder head 22 and the cylinder block 23 is smaller than the cross-sectional area S2 of the flow path F2 connecting between the exhaust manifold 24 and the cylinder head 22. However, the present invention is not limited to this. In the present invention, the cooling flow path may be configured such that the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block is the same as, or larger than, the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head.

[0088] Further, in the above embodiment, an example is shown in which the cooling flow path 50 is configured such that a part of the cooling water flowing through the cylinder head 22 flows into the cylinder block 23, and the remaining part of the cooling water flowing through the cylinder head 22 is discharged to the outside of the cylinder head 22 through the upper end flow path opening 22c. However, the present invention is not limited to this. In the present invention, the cooling flow path may be configured such that a part of the cooling water flowing through the cylinder head flows into the cylinder block, another part of the cooling water flowing through the cylinder head is discharged to the outside of the cylinder head through the upper end flow path opening, and the remaining part of the cooling water flowing through the cylinder head flows into a part constituting a small ship other than the cylinder block and the flow path connected to the cylinder block via the upper end flow path opening.

[0089] In the above embodiment, an example is shown in which the cooling channel 50 is configured such that the cooling water discharged to the outside of the cylinder head 22 through the upper end portion flow port 22c is discharged to the outside of the hull 10 via the rectifier / regulator 41. However, the present invention is not limited to this. In the present invention, the cooling channel may be configured such that the cooling water discharged to the outside of the cylinder head through the upper end portion flow port is discharged to the outside of the hull without passing through the rectifier / regulator.

[0090] In the above embodiment, an example is shown in which the cooling channel 50 is configured such that the cooling water that has flowed through the cylinder head 22 is discharged to the outside of the cylinder head 22 through the upper end portion flow port 22c disposed near the upper end of the flow path portion 22a provided in the cylinder head 22. However, the present invention is not limited to this. In the present invention, the cooling channel may not be configured such that the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head through the upper end portion flow port.

[0091] In the above embodiment, an example is shown in which the cooling channel 50 is configured such that the cooling water that has flowed through the oil cooler 27 flows into the cylinder block 23 from the lower side through the lower end portion flow port 23d. However, the present invention is not limited to this. In the present invention, the cooling channel may be configured such that the cooling water that has not flowed through the oil cooler flows into the cylinder block from the lower side through the lower end portion flow port.

[0092] In the above embodiment, an example is shown in which the small ship 100 is a water jet propulsion boat (water motorcycle). However, the present invention is not limited to this. In the present invention, the small ship may be a pleasure boat or the like.

Explanation of Reference Numerals

[0093] 10 Hull 20 Engine 22 Cylinder Head Flow path portion provided in the 22a cylinder head 22c Upper end flow path opening 23 Cylinder block 23c Outlet of cooling water (of the cylinder block) 23a Flow path portion provided in the cylinder block 23d Lower end flow path opening 24 Exhaust manifold 27 Oil cooler 30 Propulsion unit 41 Rectifier / Regulator 50 Cooling flow path 54 Thermostat 100 Small ship 110 Cooling system for marine engine F1 Flow path connecting between the cylinder head and the cylinder block F2 Flow path connecting between the exhaust manifold and the cylinder head F3 Flow path connecting between the cylinder head and the rectifier / regulator (flow path connected to the cylinder head via the upper end flow path opening) F4 Flow path connecting between the oil cooler and the cylinder block (flow path connected to the cylinder block via the lower end flow path opening) S1 Cross-sectional area (of the flow path connecting between the cylinder head and the cylinder block) S2 Cross-sectional area (of the flow path connecting between the exhaust manifold and the cylinder head) S3 Cross-sectional area (of the flow path connecting between the cylinder head and the rectifier / regulator (flow path connected to the cylinder head via the upper end flow path opening)) S4 Cross-sectional area (of the flow path connecting between the oil cooler and the cylinder block (flow path connected to the cylinder block via the lower end flow path opening))

Claims

1. A hull, an engine provided on the hull and including an exhaust manifold, a cylinder head, and a cylinder block, and a cooling flow path through which cooling water for cooling the engine flows, wherein the cooling flow path is configured such that the cooling water that has flowed through the exhaust manifold flows into the cylinder block via the cylinder head, a thermostat for adjusting the flow rate of the cooling water discharged from the cylinder block based on the temperature of the cooling water is provided near the outlet of the cooling water in the cylinder block, the cooling flow path is configured such that the cooling water flows into the cylinder block from below via a lower end flow port disposed near the lower end of a flow path portion provided in the cylinder block, a small ship.

2. the engine includes an oil cooler, the cooling flow path is configured such that the cooling water that has flowed through the oil cooler flows into the cylinder block from below via the lower end flow port, the small ship according to claim 1.

3. the cooling flow path is configured such that the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head via an upper end flow port disposed near the upper end of a flow path portion provided in the cylinder head, the small ship according to claim 1.

4. further comprising a rectifier / regulator used for controlling the engine, the cooling flow path is configured such that the cooling water discharged to the outside of the cylinder head via the upper end flow port is discharged to the outside of the hull via the rectifier / regulator, the small ship according to claim 3.

5. the cooling flow path is configured such that a part of the cooling water that has flowed through the cylinder head flows into the cylinder block, and the remaining part of the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head via the upper end flow port, the small ship according to claim 3.

6. the cooling flow path is configured such that the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block is smaller than the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head, the small ship according to claim 1.

7. The small ship according to claim 3, wherein the cooling flow path is configured such that a cross-sectional area of a flow path connected to the cylinder head via the upper end portion flow port is smaller than a cross-sectional area of a flow path connecting between the exhaust manifold and the cylinder head.

8. The small ship according to claim 3, wherein the cooling flow path is configured such that a cross-sectional area of a flow path connected to the cylinder head via the upper end portion flow port is smaller than a cross-sectional area of a flow path connecting between the cylinder head and the cylinder block.

9. The small ship according to claim 1, wherein the cooling flow path is configured such that a cross-sectional area of a flow path connected to the cylinder block via the lower end portion flow port is smaller than a cross-sectional area of a flow path connecting between the cylinder head and the cylinder block.

10. The small ship according to claim 2, wherein the cooling flow path is configured such that a part of the cooling water flowing in from the outside of the hull flows into the exhaust manifold, and the remaining part of the cooling water flowing in from the outside of the hull flows into the oil cooler.

11. The small ship according to claim 1, wherein the thermostat is configured to adjust a flow rate of the cooling water discharged from the cylinder block to a predetermined temperature at which the temperature of the cooling water is approximately 50 degrees or more and approximately 70 degrees or less.

12. The small ship according to claim 1, wherein the cooling flow path is configured such that all of the cooling water that has flowed through the exhaust manifold flows into the cylinder head.

13. The small ship according to claim 1, further comprising a jet propulsion unit that generates thrust by the driving force of the engine.

14. A cooling flow path that is provided in the hull and configured to allow cooling water for cooling an engine including an exhaust manifold, a cylinder head, and a cylinder block to flow therethrough, and the cooling water that has flowed through the exhaust manifold flows into the cylinder block via the cylinder head; A thermostat that is provided near an outlet of the cooling water of the cylinder block and adjusts a flow rate of the cooling water discharged from the cylinder block based on the temperature of the cooling water. The cooling flow path is configured such that the cooling water flows into the cylinder block from the lower side through a lower end flow path opening disposed near the lower end of the flow path portion provided in the cylinder block, for a cooling system of a marine engine.

15. The engine includes an oil cooler, The cooling flow path is configured such that the cooling water that has flowed through the oil cooler flows into the cylinder block from the lower side through the lower end flow path opening, for the cooling system of the marine engine according to claim 14.

16. The cooling flow path is configured such that the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head through an upper end flow path opening disposed near the upper end of the flow path portion provided in the cylinder head, for the cooling system of the marine engine according to claim 14.

17. A rectifier / regulator used for controlling the engine is provided on the hull, The cooling flow path is configured such that the cooling water discharged to the outside of the cylinder head through the upper end flow path opening is discharged to the outside of the hull via the rectifier / regulator, for the cooling system of the marine engine according to claim 16.

18. The cooling flow path is configured such that a part of the cooling water that has flowed through the cylinder head flows into the cylinder block, and the remaining part of the cooling water that has flowed through the cylinder head is discharged to the outside of the cylinder head through the upper end flow path opening, for the cooling system of the marine engine according to claim 16.

19. The cooling flow path is configured such that the cross-sectional area of the flow path connecting between the cylinder head and the cylinder block is smaller than the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head, for the cooling system of the marine engine according to claim 14.

20. The cooling flow path is configured such that the cross-sectional area of the flow path connected to the cylinder head through the upper end flow path opening is smaller than the cross-sectional area of the flow path connecting between the exhaust manifold and the cylinder head, for the cooling system of the marine engine according to claim 16.

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