Boat propulsion device and boat

Abstract

A boat propulsion device includes a cowl, an upper case, a lower case rotatable about a steering shaft relative to the upper case, an engine in the cowl, a propeller shaft supported by the lower case, a drive transmission in the upper case and the lower case, an electric actuator including an output shaft, and a shifter in the upper case. The drive transmission configured to selectively execute a first transmission state in which the propeller shaft is rotated in a first rotational direction and a second transmission state in which the propeller shaft is rotated in a second rotational direction opposite to the first rotational direction. The shifter is configured to switch the drive transmission between the first transmission state and the second transmission state according to a rotation of the output shaft of the actuator.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority to Japanese Patent Application No. 2024-209900 filed on Dec. 3, 2024. The entire contents of this application are hereby incorporated herein by reference.BACKGROUND OF THE INVENTION1. Field of the Invention

[0002] The technologies disclosed herein relate to boat propulsion devices and boats.2. Description of the Related Art

[0003] A well-known boat propulsion device includes a cowl that houses an engine, a lower case that supports a propeller shaft, an upper case that is disposed between the cowl and the lower case, a drive transmission device, an electric actuator, and a shift device. The drive transmission device is configured to selectively execute a first transmission state in which the propeller shaft is rotated in a first rotational direction based on a driving force of the engine, and a second transmission state in which the propeller shaft is rotated in a second rotational direction opposite to the first rotational direction based on the driving force of the engine. The actuator operates based on an operation instruction signal from an operation device provided on the boat. The shift device switches the drive transmission device between the first transmission state and the second transmission state in response to an operation of the actuator (for example, see JP 2018-086952 A, JP 2021-011180 A, and JP H 09-309496 A).

[0004] Among boat propulsion devices of this kind, there are boat propulsion devices of a lower steering type (for example, see U.S. Pat. No. 11,130,554). In this boat propulsion device of a lower steering type, the lower case is supported so as to be rotatable about an upper case steering shaft.

[0005] In known boat propulsion device of a lower steering type, disposition of the actuator and the shift device has not been sufficiently studied, and there is room for improvement.SUMMARY OF INVENTION

[0006] Example embodiments of the present invention disclose technologies capable of solving the above-described problem.

[0007] The technologies disclosed herein may be implemented, for example, as any of the following example embodiments.

[0008] A boat propulsion device according to an example embodiment of the present invention includes a cowl, an upper case below the cowl in a first direction, a lower case below the upper case in the first direction and rotatable about a steering shaft extending in the first direction relative to the upper case, an engine in the cowl, a propeller shaft supported by the lower case, a drive transmission in the upper case and the lower case and configured to selectively execute a first transmission state in which the propeller shaft is rotated in a first rotational direction, and a second transmission state in which the propeller shaft is rotated in a second rotational direction opposite to the first rotational direction, an electric actuator in the cowl and including a rotating output shaft, and a shifter in the upper case configured to switch the drive transmission between the first transmission state and the second transmission state in response to rotation of the output shaft of the actuator.

[0009] A boat propulsion device according to another example embodiment of the present invention includes a cowl, an upper case below the cowl in a first direction, a lower case below the upper case in the first direction and rotatable about a steering shaft extending in the first direction relative to the upper case, an engine in the cowl, a propeller shaft supported by the lower case, a drive transmission in the upper case and the lower case configured to selectively execute a first transmission state in which the propeller shaft is rotated in a first rotational direction, and a second transmission state in which the propeller shaft is rotated in a second rotational direction opposite to the first rotational direction, an electric actuator in the cowl and including an output shaft, and a shifter in the upper case configured to switch the drive transmission between the first transmission state and the second transmission state in response to rotation of the output shaft of the actuator.

[0010] The technologies disclosed herein can be implemented in various example embodiments, including, for example, boat propulsion devices, boats including a boat propulsion device and a boat body, or the like.

[0011] The above and other elements, features, steps, characteristics and advantages of the present invention will become more apparent from the following detailed description of the example embodiments with reference to the attached drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a perspective view schematically illustrating a configuration of a boat.

[0013] FIG. 2 is a side view schematically illustrating a configuration of an outboard motor.

[0014] FIG. 3 is an explanatory view illustrating a configuration in which an actuator, a shifter, and a drive transmission are disposed.

[0015] FIG. 4 is an explanatory view illustrating a linkage in a first transmission state.

[0016] FIG. 5 is an explanatory view illustrating a linkage in a second transmission state.DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0017] FIG. 1 is a perspective view schematically illustrating a configuration of a boat 10. In FIG. 1 and other drawings to be described below, arrows representing each direction with respect to the position of the boat 10 are illustrated as a non-limiting example. In each of the figures, arrows respectively representing front (FRONT), rear (REAR), left (LEFT), right (RIGHT), upper (UPPER), and lower (LOWER) directions are illustrated as a non-limiting example. A front-rear direction, a left-right direction, and an up-down direction (vertical direction) are orthogonal to each other. In this specification, an axis, a structural element, or the like, extending in the front-rear direction is not necessarily parallel to the front-rear direction. The axis or the structural element extending in the front-rear direction includes an axis or a structural element inclined in a range of ±45° with respect to the front-rear direction. Similarly, an axis or a structural element extending in the up-down direction includes an axis or a structural element inclined in a range of ±45° with respect to the up-down direction, and an axis or a structural element extending in the left-right direction includes an axis or a structural element inclined in a range of ±45° with respect to the left-right direction.

[0018] The boat 10 includes a boat body 200 and an outboard motor 100. In the present example embodiment, the boat 10 includes one outboard motor 100, but the boat 10 may include a plurality of outboard motors 100. The outboard motor 100 is a so-called outboard motor of a lower steering type, in which a lower case 118 supporting a propeller shaft 136 rotates relative to an upper case 117. Switching of a shift state (forward rotation state, neutral state, reverse rotation state) of the outboard motor 100 (drive transmission 140) is controlled by drive-by-wire.

[0019] The boat body 200 is a portion of the boat 10 on which an occupant rides. The boat body 200 includes a boat main body 202, a pilot seat 240, and a steering device 250. A living space 204 is provided in the boat main body 202. The pilot seat 240 is provided in the living space 204. The steering device 250 is located near the pilot seat 240. The steering device 250 steers the boat 10. The steering device 250 includes, for example, a steering wheel 252, a shift / throttle lever 254, a monitor 256, and an input device 258. The boat body 200 includes a partition wall 220 and a transom 210. The partition wall 220 defines a space on the rear end of the living space 204. The transom 210 is located at the rear end of the boat body 200. In the front-rear direction, a space 206 is provided between the transom 210 and the partition wall 220.

[0020] FIG. 2 is a side view schematically illustrating a configuration of the outboard motor 100. The outboard motor 100 in a reference attitude will be described below unless otherwise noted. The reference attitude is an attitude in which a rotation axis Ac of a drive shaft 132 to be described below extends in the up-down direction and a rotation axis Ap of a propeller shaft 136 to be described below extends in the front-rear direction. The front-rear direction, the left-right direction, and the up-down direction are defined based on the outboard motor 100 in the reference attitude. The outboard motor 100 is an example of a boat propulsion device. The up-down direction of the outboard motor 100 in the reference attitude is an example of a first direction.

[0021] The outboard motor 100 generates a thrust to propel the boat 10. The outboard motor 100 is attached to the transom 210 at a rear portion of the boat body 200. The outboard motor 100 includes an outboard motor main body 110 and a suspension device 150.

[0022] The outboard motor main body 110 includes an engine assembly 120, a cowl 112, a casing 116, a propeller shaft 136, a propeller 111, a drive transmission 140, a shift actuator 170, and a shifter 180.

[0023] The engine assembly 120 includes a plurality of components including an engine body 122. The engine assembly 120 includes an intake system 126 (for example, a throttle body, a supercharger, etc.) and an electrical component 128 (for example, a fuse box, an ECU, a steering CU, etc.) in addition to the engine body 122. The engine assembly 120 is located in a relatively high in the outboard motor 100.

[0024] The engine body 122 includes an engine that generates power. The engine body 122 may be, for example, an internal combustion engine. The engine body 122 includes a crankshaft that converts reciprocating motion of a piston (not illustrated) into rotational motion.

[0025] The cowl 112 is a housing body disposed in an upper portion of the outboard motor main body 110. The cowl 112 includes an upper cowl 113 and a lower cowl 114. The upper cowl 113 defines an upper portion of the cowl 112. The lower cowl 114 defines a lower portion of the cowl 112. The upper cowl 113 is removably attached to the lower cowl 114. The cowl 112 houses at least a portion of the engine assembly 120.

[0026] The casing 116 is a housing body disposed in a lower portion of the outboard motor main body 110. The casing 116 is located below the cowl 112. The casing 116 includes an upper case 117 and a lower case 118. The upper case 117 defines an upper portion of the casing 116. The lower case 118 defines a lower portion of the casing 116. The lower case 118 is rotatable about a steering shaft (coaxial with the rotation axis Ac) extending in the up-down direction relative to the upper case 117. That is, the outboard motor 100 is configured to be steered by a lower steering system. The lower case 118 is configured to be rotatable by 180 degrees or more around the steering shaft relative to the upper case 117.

[0027] The propeller shaft 136 is a rod-shaped member. The propeller shaft 136 is disposed relatively low in the outboard motor main body 110 in an attitude in which a rotation axis Ap thereof extends in the front-rear direction. A front end portion of the propeller shaft 136 is housed in the lower case 118. A rear end portion of the propeller shaft 136 protrudes rearward from the lower case 118.

[0028] The propeller 111 is a rotating member including a plurality of blades. The propeller 111 is attached to the rear end portion of the propeller shaft 136. The propeller 111 rotates together with the propeller shaft 136. By rotating, the propeller 111 generates a thrust for the boat 10.

[0029] The drive transmission 140 transmits a driving force of the engine body 122 to the propeller shaft 136. The drive transmission 140 includes a drive shaft 132, a first transmission device 160, and a second transmission device 190.

[0030] The drive shaft 132 is a rod-shaped member extending in the up-down direction. An upper end portion of the drive shaft 132 is located in the upper case 117, and a lower end portion of the drive shaft 132 is located in the lower case 118. The upper case 117 and the lower case 118 support the drive shaft 132 so as to be rotatable about a rotation axis Ac thereof.

[0031] The second transmission device 190 is housed in the lower case 118. The second transmission device 190 is located below the drive shaft 132. The second transmission device 190 transmits the driving force of the engine body 122 from the drive shaft 132 to the propeller shaft 136. The second transmission device 190 includes a fourth gear 191 and a fifth gear 193. The fourth gear 191 is a drive gear, and the fifth gear 193 is a driven gear.

[0032] The fourth gear 191 is a tubular gear that surrounds the lower end portion of the drive shaft 132. The fourth gear 191 is connected to the lower end portion of the drive shaft 132. The fourth gear 191 is rotated together with the drive shaft 132 by the driving force of the engine body 122. A rotation axis of the fourth gear 191 is parallel to the up-down direction. The fifth gear 193 is a tubular gear that surrounds the front end portion of the propeller shaft 136. A rotation axis of the fifth gear 193 is parallel to the rotation axis Ap of the propeller shaft 136. In other words, the rotation axis of the fifth gear 193 is parallel to the horizontal direction and perpendicular to the rotation axis of the fourth gear 191. The fifth gear 193 meshes with the fourth gear 191. Thus, the driving force of the engine body 122 is transmitted to the fifth gear 193 via the fourth gear 191.

[0033] The first transmission device 160 is housed in the upper case 117. The first transmission device 160 is located above the drive shaft 132. The first transmission device 160 transmits the driving force of the engine body 122 to the drive shaft 132. The first transmission device 160 includes a first gear 161, a second gear 162, a third gear 163, and a dog clutch 164. The first gear 161 is a drive gear, and each of the second gear 162 and the third gear 163 is a driven gear.

[0034] The first gear 161 is connected to a distal end portion of an output shaft 123 that rotates in conjunction with the crankshaft of the engine body 122. The first gear 161 is rotated together with the output shaft 123 by the driving force of the engine body 122. A rotation axis of the output shaft 123 is parallel to the horizontal direction. A rotation axis of the first gear 161 is parallel to the rotation axis of the output shaft 123. In other words, the rotation axis of the first gear 161 is parallel to the horizontal direction.

[0035] The second gear 162 and the third gear 163 are tubular gears that surround the upper end portion of the drive shaft 132. Rotation axes of the second gear 162 and the third gear 163 are parallel to the rotation axis Ac of the drive shaft 132. In other words, the rotation axes of the second gear 162 and the third gear 163 are parallel to the up-down direction and perpendicular to the rotation axis of the first gear 161. Each of the second gear 162 and the third gear 163 meshes with the first gear 161. Thus, the driving force of the engine body 122 is transmitted to the second gear 162 and the third gear 163 via the first gear 161.

[0036] The dog clutch 164 is disposed between the second gear 162 and the third gear 163 in the up-down direction. The dog clutch 164 is tubular and surrounds the upper end portion of the drive shaft 132. The dog clutch 164 is connected to the drive shaft 132 by, for example, a spline. The dog clutch 164 rotates together with the drive shaft 132.

[0037] The dog clutch 164 is movable in the up-down direction. More specifically, the dog clutch 164 is movable between a first connection position where it is connected to the second gear 162, a second connection position where it is connected to the third gear 163, and a disconnection position where it is separated from the second gear 162 and the third gear 163. When the dog clutch 164 is in the first connection position, the rotation of the second gear 162 is transmitted to the dog clutch 164, and the rotation of the dog clutch 164 is transmitted to the drive shaft 132. As a result, the propeller 111 rotates in the first rotational direction in which the boat 10 moves forward. A forward transmission state, in which the drive transmission 140 rotates the propeller 111 in the first rotational direction, is an example of a first transmission state. When the dog clutch 164 is in the second connection position, the rotation of the third gear 163 is transmitted to the dog clutch 164, and the rotation of the dog clutch 164 is transmitted to the drive shaft 132. As a result, the propeller 111 rotates in the second rotational direction in which the boat 10 moves backward. A reverse transmission state, in which the drive transmission 140 rotates the propeller 111 in the second rotational direction, is an example of a second transmission state. When the dog clutch 164 is in the disconnection position, the rotations of the second gear 162 and the third gear 163 are not transmitted to the dog clutch 164. Thus, the propeller 111 does not receive the driving force of the engine body 122. That is, when the dog clutch 164 is in the disconnection position, the outboard motor 100 is in the neutral state.

[0038] Details of the shift actuator 170 and the shifter 180 will be described below.

[0039] The suspension device 150 suspends the outboard motor main body 110 from the boat body 200. The suspension device 150 includes a pair of left and right clamp brackets 152, a tilt shaft 154, and a swivel bracket 156.

[0040] The pair of left and right clamp brackets 152 are disposed on the rearward side of the boat body 200, spaced apart from each other in the left-right direction and are secured to the transom 210 of the boat body 200 with bolts, for example. Each of the clamp brackets 152 includes a tubular support portion 153 in which a through-hole extending in the left-right direction is formed.

[0041] The tilt shaft 154, which is a rod-like body, is rotatable in the through-hole of the support portion 153 of the clamp bracket 152. A tilt axis At, which is the center line of the tilt shaft 154, constitutes an axis in the horizontal direction (left-right direction) during a tilting action of the outboard motor 100.

[0042] The swivel bracket 156 is sandwiched between the pair of clamp brackets 152, and is supported by the support portion 153 of the clamp bracket 152 via the tilt shaft 154 so as to be rotatable around the tilt axis At. The swivel bracket 156 is rotationally driven around the tilt axis At relative to the clamp bracket 152 by a tilt device (not illustrated) including an actuator such as a hydraulic cylinder.

[0043] When the swivel bracket 156 rotates around the tilt axis At relative to the clamp bracket 152, the outboard motor main body 110 supported by the swivel bracket 156 also rotates around the tilt axis At. As a result, a tilting action in which the outboard motor main body 110 is rotated in the up-down direction relative to the boat body 200 is performed. The tilting action of the outboard motor 100 may change an angle of the outboard motor main body 110 around the tilt axis At in a range from a tilt-down state where the propeller 111 is located in water (the state where the outboard motor 100 is in the reference attitude) to a tilt-up state where the propeller 111 is located above the water surface. A trim action may also be performed to adjust the angle of the outboard motor main body 110 around the tilt axis At and thus adjust the attitude of the boat 10 during traveling.

[0044] The shift actuator 170 is housed in the cowl 112. Therefore, for example, compared to a configuration in which the shift actuator 170 is disposed in the lower case 118, a wiring structure of the shift actuator 170 can be simplified. The shift actuator 170 may be an electric actuator, and is communicably connected to the steering device 250 via, for example, an electric wire (not illustrated). For example, the steering device 250 transmits an operation instruction signal corresponding to the operation of the shift / throttle lever 254 to the shift actuator 170.

[0045] The shift actuator 170 includes an electric motor (not illustrated) and an output shaft 172 that is rotated by a driving force of the electric motor. The shift actuator 170 rotates the output shaft 172 based on the received operation instruction signal. The shift actuator 170 is an example of an actuator. The shift actuator 170 is located between the engine body 122 and the upper case 117 in the up-down direction. Therefore, an increase in size of the cowl 112 in the horizontal direction is prevented or reduced by the presence of the shift actuator 170. The output shaft 172 extends along the horizontal direction. Therefore, for example, compared to a configuration in which the output shaft 172 extends along the up-down direction, the space to accommodate the shift actuator 170 in the up-down direction is reduced.

[0046] The shifter 180 is housed in the upper case 117. The shifter 180 switches the drive transmission 140 between a forward rotation state, a neutral state, and a reverse rotation state in accordance with the rotation of the output shaft 172 of the shift actuator 170.

[0047] The shifter 180 includes a shift rod 187 and a linkage 181 having an open loop configuration.

[0048] The shift rod 187 is located in the upper case 117, and is swingable about a swing shaft 188 parallel to the output shaft 172 of the shift actuator 170. In the present example embodiment, the swing shaft 188 is located directly below the output shaft 172. A distal end of the shift rod 187 is connected to an upper end portion of a support member 165. A lower end portion of the support member 165 is connected to the dog clutch 164. As a result, the dog clutch 164 moves up and down due to the swinging of the shift rod 187.

[0049] The linkage 181 includes a first link 182, a second link 183, and a third link 184. One end of the first link 182 is connected to the output shaft 172, and another end of the first link 182 swings about the output shaft 172. One end of the second link 183 is joined to the shift rod 187, and rotates integrally with the shift rod 187 about the swing shaft 188. The other end of the second link 183 swings about the swing shaft 188. An upper end portion of the third link 184 is rotatably coupled to another end portion of the first link 182 via a first rotation shaft L1. A lower end portion of the third link 184 is rotatably coupled to another end portion of the second link 183 via a second rotation shaft L2.

[0050] With such a configuration, as the output shaft 172 of the shift actuator 170 rotates, the dog clutch 164 moves in the up-down direction via the linkage 181, and the shift state of the drive transmission 140 is switched. For example, as illustrated in FIG. 5, when the output shaft 172 rotates counterclockwise in the drawing, the other end portion of the first link 182 rotates counterclockwise, and accordingly, the third link 184 moves upward. When the third link 184 moves upward, the second link 183 rotates counterclockwise about the swing shaft 188, and accordingly, the shift rod 187 pushes the support member 165 downward. As a result, the dog clutch 164 moves from the first connection position to the disconnection position or the second connection position, and the drive transmission 140 is switched from the forward rotation state to the neutral state or the reverse rotation state.

[0051] A length M1 of the first link 182 and a length M2 of the second link 183 may be equal to each other. The length M1 of the first link 182 is a straight-line distance from the center of the output shaft 172 to the center of the first rotation shaft L1. The length M2 of the second link 183 is a straight-line distance from the center of the swing shaft 188 to the center of the second rotation shaft L2.

[0052] The output shaft 172 of the shift actuator 170 and the swing shaft 188 of the shift rod 187 are parallel to each other. Therefore, for example, compared to a configuration in which the output shaft 172 and the swing shaft 188 are perpendicular to each other, it is possible to prevent or reduce an increase in complexity of the configuration of the relay (the linkage 181) that transmits power of the output shaft 172 to the swing shaft 188. At least a portion of the swing shaft 188 is disposed at a position overlapping the shift actuator 170 when viewed in the up-down direction. Thus, according to the present example embodiment, for example, an increase in size of the shifter 180 in the horizontal direction can be prevented or reduced compared to a configuration in which the swing shaft 188 does not overlap the shift actuator 170 as viewed in the up-down direction.

[0053] The technologies disclosed herein are not limited to the example embodiments described above, but can be modified in various ways without departing from the spirit thereof. For example, the following modifications are also possible.

[0054] The configurations of the boat 10 and the outboard motor 100 in the above-described example embodiments are merely examples, and various modifications are possible. For example, in the above-described example embodiments, the outboard motor 100 is exemplified as the boat propulsion device, but the boat propulsion device may be, for example, an inboard motor or a jet propeller.

[0055] In the example embodiments described above, the outboard motor 100 preferably includes only the engine as a drive source, but the boat propulsion device may be a hybrid type including a motor in addition to the engine. In the above-described example embodiments, the lower case 118 may be configured to be rotatable relative to the upper case 117 within an angular range of less than 180 degrees around the steering shaft.

[0056] In the above-described example embodiments, the shift actuator 170 may be housed in the cowl 112, and may be disposed, for example, at a position aligned with the engine body 122 in the horizontal direction. The output shaft 172 of the shift actuator 170 may extend not only in the horizontal direction but also, for example, along the up-down direction (downward). In the above-described example embodiments, the swing shaft 188 may be configured not to overlap the shift actuator 170 as viewed in the up-down direction.

[0057] In the above-described example embodiments, the linkage 181 having an open loop configuration is exemplified as the relay. However, the relay may be a linkage having another configuration such as a closed loop configuration, and may further include a belt device, a gear device, or the like.

[0058] In the above-described example embodiments, the length M1 of the first link 182 may be longer than the length M2 of the second link 183. As a result, a moving distance of the dog clutch 164 can be relatively increased relative to a predetermined rotation angle range of the output shaft 172 of the shift actuator 170. Further, in the above-described example embodiments, the length M1 of the first link 182 may be shorter than the length M2 of the second link 183. As a result, the moving distance of the dog clutch 164 can be relatively shortened relative to the predetermined rotation angle range of the output shaft 172 of the shift actuator 170.

[0059] While example embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.

Claims

1. A boat propulsion device comprising:a cowl;an upper case below the cowl in a first direction;a lower case below the upper case in the first direction and rotatable about a steering shaft extending in the first direction relative to the upper case;an engine in the cowl;a propeller shaft supported by the lower case;a drive transmission in the upper case and the lower case and configured to selectively execute a first transmission state in which the propeller shaft is rotatable in a first rotational direction, and a second transmission state in which the propeller shaft is rotatable in a second rotational direction opposite to the first rotational direction;an electric actuator in the cowl and including a rotating output shaft; anda shifter in the upper case configured to switch the drive transmission between the first transmission state and the second transmission state in accordance with rotation of the output shaft of the actuator.

2. The boat propulsion device according to claim 1, wherein the output shaft of the actuator extends in a direction perpendicular to the first direction.

3. The boat propulsion device according to claim 1, wherein the shifter includes:a shift rod configured to swing about a swing shaft parallel to the output shaft of the actuator; anda relay to transmit power of the output shaft to the swing shaft.

4. The boat propulsion device according to claim 3, wherein the relay includes a linkage having an open loop configuration.

5. The boat propulsion device according to claim 4, wherein the linkage includes:a first link connected to the output shaft and a second link connected to the swing shaft; anda length of the first link is longer than a length of the second link.

6. The boat propulsion device according to claim 4, wherein the linkage includes:a first link connected to the output shaft and a second link connected to the swing shaft; anda length of the first link is shorter than a length of the second link.

7. The boat propulsion device according to claim 3, wherein at least a portion of the swing shaft overlaps the actuator when viewed in the first direction.

8. The boat propulsion device according to claim 1, wherein the actuator is located between the engine and the upper case.

9. The boat propulsion device according to claim 1, wherein the lower case is rotatable by 180 degrees or more around the steering shaft relative to the upper case.

10. A boat comprising:a boat body; andthe boat propulsion device according to claim 1 attached to a rear portion of the boat body.

11. A boat propulsion device comprising:a cowl;an upper case below the cowl in a first direction;a lower case below the upper case in the first direction and rotatable about a steering shaft extending in the first direction relative to the upper case;an engine in the cowl;a propeller shaft supported by the lower case;a drive transmission in the upper case and the lower case and configured to selectively execute a first transmission state in which the propeller shaft is rotatable in a first rotational direction, and a second transmission state in which the propeller shaft is rotatable in a second rotational direction opposite to the first rotational direction;an electric actuator in the cowl and including an output shaft; anda shifter in the upper case configured to switch the drive transmission between the first transmission state and the second transmission state in accordance with rotation of the output shaft of the actuator.

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