Marine outboard motor with drive shaft and cooling system

Abstract

The marine outboard motor of the present invention comprises: a housing (6) having chambers (52, 53) and at least one inlet (45, 47) arranged to be submerged in use in a body of water in which the marine outboard motor operates to draw water into the chambers; an engine assembly having an internal combustion engine (100); and a drive shaft (27) arranged within the housing, the drive shaft being connected to the internal combustion engine to drive a propulsion device (8); a cooling system for cooling the internal combustion engine, the cooling system being configured to convey drawn water through the housing along a coolant flow path (43) for delivery to the internal combustion engine; and a sleeve (59) that seals the drive shaft from water drawn into the housing, at least a portion of the drive shaft being housed within the sleeve.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present application relates to marine outboard motors, although the teachings are applicable to any other internal combustion engine. [Background technology]

[0002] To propel a watercraft, an outboard motor is often mounted at the stern of the vessel. An outboard motor is generally formed in three sections: an upper motor having an internal combustion engine, a lower section having a propeller hub connected to the internal combustion engine via a drive shaft, and a middle section defining an exhaust gas flow passage for transporting exhaust gases from the upper section to the lower section.

[0003] The limited space available within the cowling can increase the cooling demands of an internal combustion engine. This is primarily because the close fit of the cowling can limit the dissipation of heat generated by the engine to the surroundings. High operating temperatures within an internal combustion engine can impair the performance and durability of the engine. It is therefore important to ensure that the engine is adequately cooled.

[0004] The housing of the marine outboard motor has one or more openings intended for submersion in use in the body of water in which the marine outboard motor is operated, thereby drawing water into a chamber within the housing (i.e., within the intermediate portion) during operation. To ensure sufficient cooling, the marine outboard motor typically has an open-circuit cooling system. A water pump is provided to convey at least a portion of the water drawn into the chamber within the marine outboard motor housing along a flow path to at least one coolant passage within the internal combustion engine to extract heat from the internal combustion engine before returning to the body of water via one or more drains.

[0005] In known systems, water drawn into the chamber within the housing flows over the surfaces of the drive shaft, resulting in degradation of the drive shaft, for example, by corrosion. To minimize this degradation, different portions of the drive shaft may be formed from different materials that are then welded together. The portions of the drive shaft that are exposed to water are often formed from a corrosion resistant material (e.g., stainless steel) with unexposed portions formed from a relatively high strength material (e.g., high strength steel). This composite welded construction of the drive shaft increases manufacturing costs of the drive shaft and can result in suboptimal drive shaft mechanical properties. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE PRESENT EMBODIMENT The present invention seeks to provide an improved marine outboard motor that overcomes or mitigates one or more problems associated with the prior art. [Means for solving the problem]

[0007] According to a first aspect of the present invention, there is provided an outboard motor for a marine vehicle comprising: a housing having a chamber and at least one inlet arranged to be submerged in use in a body of water in which the marine outboard motor operates for drawing water into the chamber; an engine assembly having an internal combustion engine; a drive shaft arranged within the housing, the drive shaft coupled to the internal combustion engine for driving a propulsion device; a cooling system for cooling the internal combustion engine, the cooling system configured to convey drawn water along a coolant flow path through the housing to deliver the drawn water to the internal combustion engine; and a sleeve, the drive shaft being sealed from the drawn water in the housing by the sleeve, the sleeve having a first end and a second end, at least a portion of the drive shaft being received within the sleeve.

[0008] Traditionally, the drive shaft is located in line with the coolant flow path, which ensures that the drive shaft is sealed away from the coolant flow path, thus reducing interaction between the drive shaft and the drawn water.

[0009] Providing a drive shaft sealed away from the coolant flow path prevents interaction of the drive shaft with water from the body of water in which the marine outboard motor operates during use, thereby reducing corrosion of the drive shaft caused by interaction of drawn-in water with the drive shaft. This allows a wider range of materials to be used to manufacture the drive shaft, thereby allowing for the use of less expensive materials.

[0010] Previous systems required a dynamic seal on the drive shaft to prevent water from the body of water in which the marine outboard motor is operating during use from leaking into the rest of the marine outboard motor, for example, into the transmission. Sealing the drive shaft from the coolant flow passages eliminates the need for a dynamic seal on the drive shaft.

[0011] The sleeve may be secured within the housing such that the drive shaft is rotatable relative to the sleeve.

[0012] Providing a stationary sleeve within the housing (with the drive shaft rotating within) eliminates the need for a dynamic seal between the sleeve and the housing, which is more reliable than a dynamic seal.

[0013] The sleeve may include multiple sleeve sections, each sleeve section receiving a different portion of the drive shaft.

[0014] This configuration advantageously allows the material of the sleeve to vary along different portions of the drive shaft, which reduces the cost of the sleeve and makes it easier to manufacture.

[0015] The housing may include an exhaust system connected to the engine assembly by an adapter plate. The first end of the sleeve may be sealingly coupled to the adapter plate.

[0016] A sealing arrangement at the first end (ie, the upper end) of the sleeve to the adapter plate prevents the drawn water from leaking into the engine assembly.

[0017] The first sleeve portion is capable of sealingly connecting the housing to the adapter plate.

[0018] The first sleeve portion may be integrally, for example integrally cast, with the housing.

[0019] Providing a portion of the sleeve integrally formed with the housing reduces the weight of the marine outboard motor.

[0020] The water pump drive mechanism may be disposed within the pump drive mechanism housing, and the second sleeve portion may be sealingly coupled between the first sleeve portion and the pump drive mechanism housing.

[0021] This arrangement advantageously ensures that the arrangement for driving the water pump (ie the impeller) is also sealed away from the water flowing through the coolant flow passage.

[0022] The marine outboard motor can include a drive transmission for the propulsion device, the drive transmission being disposed within a drive transmission housing. The second end of the sleeve can be attached to the transmission housing such that a seal is formed between the second end of the sleeve and the transmission housing.

[0023] This configuration of sealing the second end (ie, the lower end) of the sleeve to the drive transmission prevents drawn water from leaking into the drive transmission.

[0024] The water pump drive mechanism may be disposed within the pump drive mechanism housing. The third sleeve portion may be sealingly coupled between the transmission housing and the pump drive mechanism housing.

[0025] The cooling system may include a water pump configured to propel drawn water along the coolant flow path.

[0026] This arrangement ensures that there is sufficient water flow to cool the internal combustion engine.

[0027] The water pump may be separate from the drive shaft and is configured to be driven by the drive shaft.

[0028] This arrangement allows the pump impeller to be driven by the drive shaft without the need for the pump to be directly mounted on the drive shaft.

[0029] The water pump may include a pump drive mechanism having a water pump drive shaft. The water pump drive shaft may be separate from the drive shaft and configured to be driven by the drive shaft.

[0030] The water pump may be coupled to the drive shaft by a pump drive mechanism having a gear ratio greater than 1:1.

[0031] The provision of a "step-up" transmission has been shown to improve cooling of the internal combustion engine by allowing the rotational speed of the impeller to be greater than the rotational speed of the drive shaft, thereby increasing the flow rate of water drawn through the cooling system.

[0032] The pump drive mechanism includes a drive gear concentrically attached to the drive shaft and a driven gear concentrically attached to the water pump drive shaft, the drive gear and the driven gear being in meshing engagement with each other.

[0033] Providing a drive gear rotatably fixed to the drive shaft ensures that the motive force transmitted by the drive shaft can be used to drive the cooling system.

[0034] The drive shaft may extend vertically.

[0035] The internal combustion engine may be a diesel engine.

[0036] The engine block may comprise a single cylinder, but preferably the engine block comprises multiple cylinders.

[0037] As used herein, "engine block" refers to a solid structure in which at least one cylinder of an engine is located. The term may refer to the combination of the cylinder block with the cylinder head and crankcase or to the cylinder block alone. An engine block may be formed from a single engine block casting. An engine block may be formed from multiple separate engine block castings that are connected together, for example, with bolts.

[0038] The engine block may include a single cylinder bank.

[0039] The engine block may include a first cylinder bank and a second cylinder bank. The first cylinder bank and the second cylinder bank may be arranged in a V-configuration.

[0040] The engine block may have three cylinder banks. The three cylinder banks may be arranged in a sector configuration. The engine block may have four cylinder banks. The four cylinder banks may be arranged in a W configuration or in two V configurations.

[0041] The internal combustion engine may be arranged in any suitable orientation. Preferably, the internal combustion engine is a vertical axis internal combustion engine, in which the internal combustion engine has a crankshaft mounted vertically within the engine.

[0042] The internal combustion engine may be a petrol engine. Preferably, the internal combustion engine is a diesel engine. The internal combustion engine may be a turbocharged diesel engine.

[0043] According to a second aspect of the present invention, there is provided a marine vessel equipped with the marine outboard motor of the first aspect.

[0044] Within the scope of this application, the various aspects, embodiments, examples and alternatives set out in the claims and / or in the following description and drawings, in the preceding paragraphs, in particular their individual features, are expressly intended to be understood independently or in any combination. That is, all embodiments and / or features of any embodiment may be combined in any manner and / or combination, provided that the combined features are not incompatible. The applicant reserves the right to modify the originally filed claims or to file new claims, including the right to amend the originally filed claims to depend on and / or incorporate any features of other claims, even if not originally claimed.

[0045] Further features and advantages of the invention will be further explained hereinafter, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0046] [Figure 1] FIG. 1 is a schematic side view of a small boat equipped with an outboard motor for boats. [Figure 2a] FIG. 2a shows a schematic diagram of a marine outboard motor in a tilted position. [Figure 2b] FIG. 2b illustrates one of various aligned positions of a marine outboard motor and the corresponding orientation of the watercraft within the body of water. [Figure 2c] FIG. 2c illustrates one of various aligned positions of the marine outboard motor and the corresponding orientation of the watercraft within the body of water. [Figure 2d] FIG. 2d illustrates one of various aligned positions of a marine outboard motor and the corresponding orientation of the watercraft within the body of water. [Diagram 3] FIG. 3 is a schematic cross-sectional view of an outboard motor for a marine vessel according to one embodiment. [Figure 4] FIG. 4 shows a schematic cross-section of the middle and lower portions of the marine outboard motor of FIG. [Diagram 5] FIG. 5 shows an enlarged view of area A of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] Referring initially to FIG. 1, a schematic side view of a marine vessel 1 with a marine outboard motor 2 is shown. The marine vessel 1 may be any type of vessel suitable for use with a marine outboard motor, such as a ferry or a scuba diving boat. The marine outboard motor 2 shown in FIG. 1 is mounted at the stern of the marine vessel 1. The marine outboard motor 2 is typically connected to a fuel tank 3 received within the hull of the marine vessel 1. Fuel from a reservoir or fuel tank 3 is supplied to the marine outboard motor 2 via a fuel line 4. The fuel line 4 may collectively include one or more filters, a low pressure pump, and a separator tank (to prevent water from entering the marine outboard motor 2) disposed between the fuel tank 3 and the marine outboard motor 2.

[0048] The marine outboard motor 2 comprises a housing 6 in which the various components of the marine outboard motor 2 are housed. As will be explained in more detail below, the marine outboard motor 2 is generally divided into three sections: an upper section 21, a middle section 22 and a lower section 23. The middle section 22 and the lower section 23 are often collectively known as the leg, which houses the exhaust system. A propulsion arrangement is provided having a propeller 8. The propeller 8 is rotatably disposed on a propeller shaft in the lower section 23, also referred to as the gearbox of the marine outboard motor 2. Of course, during operation, the propeller 8 is at least partially submerged in water and can be operated at various rotational speeds to propel the marine vessel 1.

[0049] Typically, the marine outboard motor 2 is pivotally connected to the stern of the boat 1 by a pivot pin. Rotation about the pivot pin allows an operator to tilt and position the marine outboard motor 2 about a horizontal axis in a known manner. Additionally, as is well known in the art, the marine outboard motor 2 is pivotally mounted to the stern of the boat 1 such that it can rotate about a generally upright axis to steer the boat 1.

[0050] Tilting is the movement of raising the marine outboard motor 2 sufficiently so that the entire marine outboard motor 2 can rise completely out of the water. The tilting movement of the marine outboard motor 2 can be performed with the marine outboard motor 2 turned off or in neutral. However, in some examples, the marine outboard motor 2 may be configured to allow limited operation of the marine outboard motor 2 in a tilting range to allow operation in shallow waters. Thus, the marine engine assembly is primarily operated with the longitudinal axis of the legs substantially vertical. The engine crankshaft of the marine outboard motor 2, which is substantially parallel to the longitudinal axis of the legs of the marine outboard motor 2, will be generally oriented vertically during normal operation of the marine outboard motor 2, but may be oriented non-vertically under certain operating conditions, particularly when operated on a marine vessel in shallow water. The crankshaft of the marine outboard motor 2, which is oriented substantially parallel to the longitudinal axis of the legs of the engine assembly, may also be referred to as a vertical crankshaft arrangement. Additionally, the crankshaft of the marine outboard motor 2 being oriented substantially perpendicular to the longitudinal axis of the engine assembly leg may also be referred to as a horizontal crankshaft arrangement.

[0051] As previously mentioned, to operate properly, the lower section 23 of the marine outboard motor 2 needs to extend into the water. However, in very shallow waters or when launching the boat from a trailer, if the lower section 23 of the marine outboard motor 2 is in a tilted downward position, it may drag on the ocean bottom or cause the boat to tilt. By tilting the marine outboard motor 2 to a tilted upward position, such as the position shown in FIG. 2a, damage to the lower section 23 and the propeller 8 is prevented.

[0052] In contrast, alignment is a mechanism for moving the marine outboard motor 2 over a relatively small range, a few degrees upward from a fully lowered position, as shown in the three examples of Figures 2b-2d. Alignment helps to direct the propeller 8 thrust in a direction that provides the best combination of fuel economy, acceleration, and high speed operation of the boat 1.

[0053] When the vessel 1 is on a flat surface (when the weight of the vessel 1 is supported primarily by hydrodynamic lift rather than hydrostatic lift), the bow-up configuration provides less drag and greater stability and efficiency. This is typically the case when the centerline of the boat or vessel 1 is angled upwards by approximately 3°-5°, for example as shown in FIG. 2b.

[0054] Too much tilt will result in the bow of vessel 1 being too high in the water, such as the position shown in Figure 2c. In this configuration, the hull of vessel 1 is pushing through the water, resulting in more air resistance, and therefore reduced performance and economy. Too much upward tilt can also cause the propeller to vent, further reducing performance. In more severe cases, vessel 1 may splash through the water, throwing the operator and passengers overboard.

[0055] A downward tilt lowers the bow of vessel 1, helping it accelerate off the ground. Too much downward tilt, as shown in Figure 2d, causes vessel 1 to "plough" through the water, reducing fuel economy and making it harder to gain speed. At high speeds, a downward tilt can even make vessel 1 unstable.

[0056] 3, there is shown a schematic cross-section of a marine outboard motor 2 according to one embodiment of the present invention. The marine outboard motor 2 is provided with a tilt and position adjustment mechanism 10 for performing the tilt and position adjustment operation described above. In this embodiment, the tilt and position adjustment mechanism 10 has a fluid pressure actuator 11 that can be actuated via an electrical control system to tilt and position the marine outboard motor 2. Alternatively, it is feasible to provide a manual tilt and position adjustment mechanism in which an operator rotates the marine outboard motor 2 by hand rather than using a hydraulic actuator.

[0057] As described above, the marine outboard motor 2 is generally divided into three sections. The upper section 21, also known as the engine, houses an engine assembly having an internal combustion engine 100 for powering the marine vessel 1. A cowling section 25 is disposed around the internal combustion engine 100. The cowling section 25 may form part of the housing 6. The cowling section 25 may be provided as a separate component that is removably connected to the housing 6. The housing 6 forms a housing around the legs, and the cowling section houses the upper section 21 of the marine outboard motor 2.

[0058] The engine includes an intermediate portion 22 and a lower portion 23 extending downward adjacent to the upper portion 21 or engine. The lower portion 23 extends downward adjacent to the intermediate portion 22, which connects the upper portion 21 to the lower portion 23. The intermediate portion 22 houses a drive shaft 27 extending between the internal combustion engine 100 and a propeller shaft 29. The drive shaft 27 is connected at its upper end to a crankshaft 31 of the internal combustion engine via a floating connector 33 (e.g., a splined connection). A gearbox or drive transmission is provided at the lower end of the drive shaft 27 for horizontally transferring the rotational energy of the drive shaft 27 to the propeller 8. The gearbox or drive transmission comprises a transmission housing 61. More specifically, the bottom end of the drive shaft 27 may have a bevel gear 35 connected to a pair of bevel gears 37, 39 which are rotationally connected to the propeller shaft 29 of the propeller 8.

[0059] The middle section 22 and the lower section 23 form an exhaust system that defines an exhaust gas flow path for transporting exhaust gases from the internal combustion engine 100 and exhaust gases from the marine outboard motor 2. The exhaust system is connected to the engine assembly by an adapter plate 41 to which the internal combustion engine 100 is mounted.

[0060] As shown diagrammatically in Figure 3, the marine outboard motor 2 includes a cooling system which conveys water drawn from a body of water in which the marine outboard motor operates during use along a coolant flow passage 43 which extends through the housing 6 to the internal combustion engine 100. The water is propelled around the coolant flow passage 43 by at least one water pump (see Figures 4 and 5) for cooling the internal combustion engine 100.

[0061] The housing 6 of the marine outboard motor 2 has one or more openings that are intended to be submerged in use in the body of water in which the marine outboard motor 2 operates. In other words, in use, water from the body of water in which the marine outboard motor 2 operates enters the housing 6 via one or more openings in the housing 6 that are located below the waterline of the body of water in which the marine vessel 1 is stationary. In the illustrated configuration, the one or more openings are provided in the lower portion 23, as will be described below.

[0062] In the embodiment shown, the housing 6 has a first inlet 45 and a second inlet 47 in the lower portion 23. Although not shown, the housing 6 includes a third inlet and a fourth inlet on the opposite side of the housing 6 at substantially the same locations as the first inlet 45 and the second inlet 47. In alternative configurations, the coolant flow passage 43 can have any suitable number of inlets (e.g., one, two, five, etc.) and / or one or more of these inlets can be provided in the middle portion 22.

[0063] The below-waterline openings are positioned so that, in use, water in which the marine outboard motor 2 is operating is drawn into the chambers 52, 53 within the housing 6. In this manner, the chambers 52, 53 within the housing 6 are continuously provided with water drawn from the body of water in which the marine outboard motor 2 operates. As will be described in more detail below, the surface of the drive shaft 27 is sealed within the housing 6 so that the surface of the drive shaft 27 is not exposed to water drawn into the housing 6.

[0064] 4 and 5, the middle portion 22 and the lower portion 23 are shown.

[0065] In use, water from the body of water in which the marine outboard motor 2 is used enters the chambers 52, 53 of the housing 6 via the first inlet 45 and the second inlet 47. The water pump 49 has an impeller 75 configured to rotate about its central axis within a pump housing 77. The water pump 49 is supplied with water drawn from the chambers 52, 53 via the pump inlet 79.

[0066] The rotating impeller 75 accelerates the drawn water as it moves across the impeller 75, creating a pressure differential across the water pump 49. This causes a pressurized flow of the drawn water to be directed along the coolant flow path 43 via the water pump 49 to the internal combustion engine 100. To absorb heat from the internal combustion engine 100, the drawn water flows along at least one coolant passage (not shown) within the internal combustion engine 100 before returning to the body of water via one or more drains (not shown). In this manner, the cooling system is configured to draw water into the housing 6 and propel the drawn water along the coolant flow path 43 to the internal combustion engine 100.

[0067] In the embodiment shown, the water pump 49 is a centrifugal pump that is located remote from (i.e., not directly attached to) the drive shaft 27 and configured to be driven by the drive shaft 27. That is, the impeller 75 of the water pump 49 is rotated by rotation of the drive shaft 27. It will be appreciated that alternative types of water pumps may be used in the marine outboard motor 2, such as, for example, a flexible impeller pump. It will also be appreciated that in alternative configurations, the water pump 49 may be mounted directly to the drive shaft 27 or to a sleeve about the drive shaft 27, as will be described in more detail below.

[0068] To drive the water pump 49, the marine outboard motor 2 has a pump drive mechanism 63 connected to the drive shaft 27. The pump drive mechanism 63 is configured to supply rotational energy of the drive shaft 27 to the water pump 49 to drive the impeller 75. The pump drive mechanism 63 is disposed within a pump drive mechanism housing 73.

[0069] In the illustrated configuration, the water pump 49 has a water pump drive shaft 71. The water pump drive shaft 71 is spaced apart from (i.e., axially offset from) the drive shaft 27 and is configured to be driven by the drive shaft 27.

[0070] In this example, the water pump 49 is coupled to the drive shaft 27 by a pump drive mechanism in the form of a drive gear 65 configured to transfer drive power from the drive shaft 27 to the water pump 49. The drive gear 65 is concentrically mounted on the drive shaft 27. The pump drive mechanism 63 further includes a driven gear 66 concentrically mounted on the water pump drive shaft 71. The drive gear 65 and the driven gear 66 are in meshing engagement such that drive power can be transferred from the drive shaft 27 to the water pump 49.

[0071] In some embodiments, the water pump 49 is coupled to the drive shaft 27 by a pump drive mechanism 63 having a gear ratio greater than 1:1. The "step-up drive" described above can be advantageous when the typical rotational speed of the drive shaft 27 cannot provide sufficient flow rate through the water pump 49, for example when the diameter of the water pump 49 is limited by available space.

[0072] The marine outboard motor 2 is constructed and arranged to prevent or at least minimize interaction between the drawn water (i.e., the drawn water in the chambers 52, 53 and the drawn water flowing along the coolant flow passages 43) and the surfaces of the drive shaft 27. This allows the entire drive shaft 27 to be manufactured from a high strength material (e.g., high strength steel) without the need to have corrosion resistant portions.

[0073] In the illustrated configuration, the marine outboard motor 2 includes a sleeve 59 that seals the drive shaft 27 from the coolant passage 43. At least a portion of the drive shaft 27 is received within the sleeve 59 to seal the drive shaft 27 from water drawn into the housing 6 (i.e., into the chambers 52, 53 and into the coolant passage 43).

[0074] In the embodiment shown, the sleeve 59 is arranged to be fixed within the housing 6. In other words, when the sleeve 59 is mounted within the housing 6, the sleeve 59 does not rotate relative to the housing 6, but the drive shaft 27 rotates within the sleeve 59 relative to the sleeve 59. In this manner, a static seal may be provided or formed between the sleeve 59 and the housing 6, improving the reliability of the sealing of the drive shaft 27 away from the coolant flow passage 43.

[0075] The sleeve 59 is attached at its lower or "second" end to the transmission housing 61 such that a seal is formed between the sleeve 59 and the transmission housing 61. In the embodiment shown, the sleeve 59 is attached at its lower end to the transmission housing 61 via threads, however, it will be appreciated that any suitable attachment configuration may be utilized to provide a seal between the sleeve 59 and the transmission housing 61.

[0076] The sleeve 59 is attached at its upper or "first" end to the adapter plate 41 such that a seal is formed between the sleeve 59 and the adapter plate 41. In the illustrated configuration, the sleeve 59 is attached at its upper end to the adapter plate 41 via a press fit (also known as an interference fit) and utilizes two O-rings 81 to provide a seal between the sleeve 59 and the adapter plate 41. It will be appreciated that any suitable attachment configuration may be utilized to provide a seal between the sleeve 59 and the adapter plate 41, for example a threaded fit.

[0077] In the illustrated example, the sleeve 59 is provided as a series of separate sections in the form of a first or upper sleeve 83, a second or middle sleeve 85 and a third or lower sleeve 87.

[0078] The first sleeve 83 is attached at its upper end to the adapter plate 41 such that a seal is formed between them. The first sleeve 83 is integral with the housing 6 of the intermediate portion 22, i.e. the first sleeve 83 is formed from the same casting as the intermediate portion 22. In the embodiment shown the intermediate portion 22 and the first sleeve 83 are formed from aluminium, although it will be understood that the material may vary depending on the application.

[0079] The second sleeve 85 is connected to the first sleeve 83. In the illustrated configuration, the second sleeve 85 is connected to the first sleeve 83 via an interference fit. That is, an upper end of the second sleeve 85 is connected to a lower end of the first sleeve via an interference fit. Although not illustrated, it will be appreciated that an O-ring may be provided to further seal the connection between the second sleeve 85 and the first sleeve 83. Furthermore, it will be appreciated that any suitable mounting arrangement may be utilized to provide a seal between the second sleeve 85 and the first sleeve 83, for example a threaded mounting arrangement.

[0080] The second sleeve 85 and the third sleeve 87 are connected to the pump drive mechanism housing 73 such that the pump drive mechanism housing 73 is interposed between the second sleeve 85 and the third sleeve 87. In this manner, the drive shaft 27 and the pump drive mechanism 63 are sealed from the coolant flow path 43.

[0081] In the embodiment shown, the second sleeve 85 is connected to the pump drive housing 73 via an interference fit such that a seal is formed between the pump drive housing 73 and the second sleeve 85. Although not shown, it will be appreciated that an O-ring may be provided to further seal the connection between the second sleeve 85 and the pump drive housing 73. It will further be appreciated that any suitable mounting arrangement may be utilized to provide a seal between the second sleeve 85 and the pump drive housing 73, for example, a threaded mounting arrangement. In the embodiment shown, the second sleeve 85 is formed from a plastic material, however it will be appreciated that any suitable material may be used, such as a copper-based alloy (e.g., bronze) or a steel alloy.

[0082] In the embodiment shown, the third sleeve 87 is integral with the gearbox or drive transmission. The third sleeve 87 is connected to the pump drive mechanism housing 73 via threads such that a seal is formed between the pump drive mechanism housing 73 and the third sleeve 87. It will be appreciated that different connection configurations, such as an interference fit, may be used. In the embodiment shown, the second sleeve 85 is formed from aluminum, but it will be appreciated that any suitable material, such as a copper-based alloy (e.g. bronze) or a steel alloy, may be used.

[0083] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications can be made without departing from the scope of the invention, as defined in the appended claims. The present disclosure also includes the following inventions. The first aspect is A marine outboard motor, comprising: a housing including a chamber and at least one inlet arranged in use to be submerged in a body of water in which the marine outboard motor operates for drawing water into the chamber; an engine assembly comprising an internal combustion engine; a drive shaft disposed within the housing, the drive shaft coupled to the internal combustion engine to drive a propulsion device; a cooling system for cooling the internal combustion engine, the cooling system being configured to convey drawn water along a coolant flow path through the housing to deliver the drawn water to the internal combustion engine; a sleeve, the sleeve sealing the drive shaft from water drawn into the housing, the sleeve having a first end and a second end; At least a portion of the drive shaft is housed within the sleeve. The second aspect is In a first aspect of the present invention, in the marine outboard motor, the sleeve is fixed within the housing such that the drive shaft is rotatable relative to the sleeve. The third aspect is In the marine outboard motor of the first or second aspect, the sleeve includes a plurality of sleeve sections, each sleeve section housing a different portion of the drive shaft. The fourth aspect is This is an outboard motor for marine use in any one of the first to third aspects, wherein the housing has an exhaust system connected to the engine assembly by an adapter plate, and a first end of the sleeve is sealingly connected to the adapter plate. The fifth aspect is In a fourth aspect of the marine outboard motor, a first sleeve portion sealingly connects the housing to the adapter plate. The sixth aspect is In a fifth aspect of the present invention, there is provided an outboard motor for marine use, wherein the first sleeve portion is formed integrally with the housing. The seventh aspect is In a sixth aspect of the present invention, there is provided an outboard motor for marine use, wherein the first sleeve portion is integrally cast with the housing. The eighth aspect is A marine outboard motor according to the fifth or sixth aspect, wherein the water pump drive mechanism is disposed within a pump drive mechanism housing, and the second sleeve portion is sealedly connected between the first sleeve portion and the pump drive mechanism housing. The ninth aspect is The outboard motor for a marine vessel is an outboard motor for a marine vessel of any one of the first to sixth aspects, comprising a drive transmission device for the propulsion device, the drive transmission device being disposed within a drive transmission device housing, and the second end of the sleeve being attached to the transmission device housing so that a seal is formed between the second end of the sleeve and the transmission device housing. A tenth aspect is A ninth aspect of an outboard motor for marine use, wherein a water pump drive mechanism is disposed within a pump drive mechanism housing, a second sleeve portion is sealingly connected between the first sleeve portion and the pump drive mechanism housing, and a third sleeve portion is sealingly connected between the transmission device housing and the pump drive mechanism housing. An eleventh aspect is The cooling system is an outboard motor for marine use described in any one of the first to seventh aspects or the ninth aspect, which is provided with a water pump configured to propel the drawn-in water along the coolant flow path. A twelfth aspect is In an eleventh aspect of the present invention, there is provided an outboard motor for marine use, wherein the water pump is separate from the drive shaft and is configured to be driven by the drive shaft. A thirteenth aspect is In a twelfth aspect of an outboard motor for marine use, the water pump is provided with a pump drive mechanism having a water pump drive shaft, the water pump drive shaft being separate from the drive shaft and configured to be driven by the drive shaft. A fourteenth aspect is In a twelfth aspect of the present invention, there is provided an outboard motor for a marine vessel, wherein the water pump is connected to the drive shaft by a pump drive mechanism having a gear ratio greater than 1:1. The fifteenth aspect is In a fourteenth aspect of the present invention, the pump drive mechanism comprises a drive gear concentrically attached to the drive shaft and a driven gear concentrically attached to the water pump drive shaft, the drive gear and the driven gear being in meshing engagement with each other. A sixteenth aspect is In the outboard motor for marine use according to any one of the first to fifteenth aspects, the drive shaft extends vertically. A seventeenth aspect is The marine outboard motor according to any one of the first to sixteenth aspects, wherein the internal combustion engine is a diesel engine. The eighteenth aspect is A boat equipped with the marine outboard motor according to any one of the first to seventeenth aspects.

Claims

1. A marine outboard motor, comprising: a housing including a chamber, an exhaust system, and at least one inlet arranged in use to be submerged in a body of water in which the marine outboard motor operates for drawing water into the chamber; an engine assembly including an internal combustion engine, the exhaust system being connected to the engine assembly by an adapter plate; a drive shaft disposed within the housing, the drive shaft coupled to the internal combustion engine to drive a propulsion device; a cooling system for cooling the internal combustion engine, the cooling system configured to convey the drawn water along a coolant flow path through the housing to deliver the drawn water to the internal combustion engine, the cooling system including a water pump separate from the drive shaft and configured to propel the drawn water along the coolant flow path; a water pump drive mechanism disposed within the pump drive mechanism housing, the water pump drive mechanism having a water pump drive shaft configured to be driven by the drive shaft; a drive transmission for the propulsion unit, the drive transmission being disposed in a drive transmission housing; a sleeve, the sleeve having a first end and a second end, the sleeve sealing the drive shaft from water drawn into the housing by a sleeve; a first sleeve portion sealingly coupled to the adapter plate; a second sleeve portion sealingly coupled between the first sleeve portion and the pump drive mechanism housing; a third sleeve portion sealingly coupled between the drive transmission housing and the pump drive mechanism housing; wherein the materials of at least two of the first sleeve portion, the second sleeve portion, and the third sleeve portion of the sleeve are different from one another such that the material of the sleeve is changed along different portions of the drive shaft.

2. 2. The marine outboard motor in accordance with claim 1, wherein said sleeve is secured within said housing such that said drive shaft is rotatable relative to said sleeve.

3. 3. The marine outboard motor according to claim 1, wherein a first sleeve portion sealingly connects said housing to said adapter plate.

4. 4. The marine outboard motor according to claim 3, wherein said first sleeve portion is formed integrally with said housing.

5. 5. The marine outboard motor of claim 4, wherein said first sleeve portion is integrally cast with said housing.

6. 6. An outboard motor for marine use according to claim 1, wherein the water pump drive mechanism has a gear ratio greater than 1:

1.

7. 7. The marine outboard motor according to claim 6, wherein the water pump drive mechanism includes a drive gear attached concentrically to the drive shaft and a driven gear attached concentrically to the water pump drive shaft, the drive gear and the driven gear being in meshing engagement with each other.

8. An outboard motor for a marine vessel as described in any one of claims 1 to 7, wherein when the longitudinal axis of the leg of the outboard motor for a marine vessel extends vertically, the drive shaft extends in a vertical direction perpendicular to a horizontal plane.

9. 9. An outboard motor for a marine vessel according to claim 1, wherein the internal combustion engine is a diesel engine.

10. A marine vessel comprising the marine outboard motor according to any one of claims 1 to 9.

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