BOAT PROPULSION DEVICE, BOAT, AND MOVABLE BODY

Abstract

A boat propulsion device includes an engine, an oil pan to store oil to be supplied to the engine, a case to accommodate at least a portion of the oil pan, and a pump to pump cooling water to a cooling water flow path in the boat propulsion device. The cooling water flow path includes a first flow path between the oil pan, the case, and the engine, and a second flow path branching from the first flow path at a location between the oil pan and the case and not extending to the engine. The boat propulsion device further includes a flow rate regulator to change at least one of a flow rate of the cooling water flowing into the first flow path and a flow rate of the cooling water flowing out of the first flow path.

Claims

1. A boat propulsion device comprising: an engine; an oil pan to store oil to be supplied to the engine; a case to accommodate at least a portion of the oil pan; and a pump to pump cooling water to a cooling water flow path in the boat propulsion device; wherein the cooling water flow path includes: a first flow path extending between the oil pan, the case, and the engine; and a second flow path branching from the first flow path at a location between the oil pan and the case and not extending to the engine; and the boat propulsion device further comprises a flow rate regulator to change at least one of a flow rate of the cooling water flowing into the first flow path and a flow rate of the cooling water flowing out of the first flow path.

2. The boat propulsion device according to claim 1, further comprising: at least one temperature sensor to measure one of a temperature in a vicinity of a combustion chamber of the engine, a temperature of an exhaust pipe through which exhaust gas discharged from the combustion chamber flows, a temperature of the oil, or a temperature of the cooling water.

3. The boat propulsion device according to claim 2, further comprising: a controller configured or programmed to control the flow rate regulator to: set the flow rate of the cooling water flowing into the first flow path to a first flow rate when the temperature measured by the at least one temperature sensor is less than a predetermined value; and set the flow rate of the cooling water flowing into the first flow path to a second flow rate, which is higher than the first flow rate, when the temperature measured by the at least one temperature sensor is equal to or more than the predetermined value.

4. The boat propulsion device according to claim 2, further comprising: a controller configured or programmed, in an idle state of the boat propulsion device, to: switch a rotation speed of the engine to a first speed when the temperature measured by the at least one temperature sensor is less than a predetermined value; and switch the rotation speed of the engine to a second speed, which is slower than the first speed, when the temperature measured by the at least one temperature sensor is equal to or more than the predetermined value.

5. The boat propulsion device according to claim 2, wherein the at least one temperature sensor includes: a first temperature sensor to measure the temperature in the vicinity of the combustion chamber; a second temperature sensor to measure the temperature of the exhaust pipe; a third temperature sensor to measure the temperature of the oil; and a fourth temperature sensor to measure the temperature of the cooling water.

6. The boat propulsion device according to claim 5, further comprising: a controller configured or programmed to control the flow rate regulator to: set the flow rate of the cooling water flowing into the first flow path to a first flow rate when the temperatures measured by the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are each less than a predetermined value; and set the flow rate of the cooling water flowing into the first flow path to a second flow rate, which is higher than the first flow rate, when the temperature measured by any of the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor is equal to or greater than the predetermined value.

7. The boat propulsion device according to claim 5, further comprising: a controller configured or programmed, in an idle state of the boat propulsion device, to: switch a rotation speed of the engine to a first speed when the temperatures measured by the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor are each less than a predetermined value; and switch the rotation speed of the engine to a second speed, which is slower than the first speed, when the temperature measured by any of the first temperature sensor, the second temperature sensor, the third temperature sensor, and the fourth temperature sensor is equal to or greater than the predetermined value.

8. The boat propulsion device according to claim 1, wherein the oil pan is located higher than the pump; and the engine is located higher than the oil pan.

9. The boat propulsion device according to claim 8, wherein the first flow path and the second flow path branch at a height lower than a lower end of the oil pan.

10. The boat propulsion device according to claim 1, wherein the flow rate regulator includes a valve.

11. The boat propulsion device according to claim 10, wherein the valve is adjustable to any valve opening degree from 0% to 100%.

12. The boat propulsion device according to claim 10, wherein the valve is located outside the case.

13. The boat propulsion device according to claim 10, wherein the valve is a three-way valve and is located inside the case; the second flow path extends downwardly in the boat propulsion device from a connection position with the valve; and an outlet of the second flow path is located at a lower portion of the boat propulsion device.

14. The boat propulsion device according to claim 10, further comprising: a device to be cooled by the cooling water; wherein the valve is a three-way valve and is located inside the case; and the second flow path extends around the device.

15. The boat propulsion device according to claim 1, wherein the first flow path contacts the oil pan.

16. The boat propulsion device according to claim 1, wherein the first flow path extends around the engine and then between the oil pan and the case.

17. The boat propulsion device according to claim 1, further comprising: an exhaust pipe located adjacent to the oil pan and through which exhaust gas discharged from the engine flows.

18. A boat comprising: a hull; and the boat propulsion device according to claim 1 mounted at a rear of the hull.

19. A movable body comprising: an engine; and an oil pan to store oil to be supplied to the engine; a case to accommodate at least a portion of the oil pan; and a pump to pump cooling water to a cooling water flow path in the movable body; wherein the cooling water flow path includes: a first flow path extending between the oil pan, the case, and the engine; and a second flow path branching from the first flow path at a location between the oil pan and the case and not extending to the engine; and the movable body further comprises a flow rate regulator to change at least one of a flow rate of the cooling water flowing into the first flow path and a flow rate of the cooling water flowing out of the first flow path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a perspective view schematically illustrating a configuration of a boat.

[0012] FIG. 2 is a side view schematically illustrating a configuration of an outboard motor.

[0013] FIG. 3 is an explanatory view illustrating a cross-sectional configuration around an oil pan in an outboard motor according to a first example embodiment of the present invention.

[0014] FIG. 4 is an explanatory view illustrating a cross-sectional configuration around the oil pan in the outboard motor according to the first example embodiment of the present invention.

[0015] FIG. 5 is a block diagram illustrating a control configuration of the outboard motor.

[0016] FIG. 6 is a flowchart illustrating a control method of a valve by a controller.

[0017] FIG. 7 is a flowchart illustrating a control method of an engine by the controller.

[0018] FIG. 8 is an explanatory view illustrating the results of performance evaluations.

[0019] FIG. 9 is an explanatory view illustrating a cross-sectional configuration around an oil pan in an outboard motor according to a second example embodiment of the present invention.

[0020] FIG. 10 is an explanatory view illustrating a cross-sectional configuration around an oil pan in an outboard motor according to a third example embodiment of the present invention.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0021] FIG. 1 is a perspective view schematically illustrating a configuration of a boat 10. FIG. 1 and the other figures described below show arrows representing each direction with respect to the position of the boat 10. More specifically, each drawing shows arrows representing the front direction (FRONT), rear direction (REAR), left direction (LEFT), right direction (RIGHT), upper direction (UPPER), and lower direction (LOWER), respectively. The front-rear direction, left-right direction, and upper-lower (vertical) direction are orthogonal to each other. It should be noted that, in this specification, axes, structures, and the like extending in the front-rear direction need not necessarily be parallel to the front-rear direction. Axes and structures extending in the front-rear direction include axes and structures inclined within the range of +45 to the front-rear direction. Similarly, axes and structures extending in the upper-lower direction include axes and structures inclined within a range of +45 to the upper-lower direction, and axes and structures extending in the left-right direction include axes and structures inclined within a range of +45 to the left-right direction.

[0022] The boat 10 includes a hull 200 and an outboard motor 100. In an example embodiment, the boat 10 includes only one outboard motor 100, but the boat 10 may include a plurality of outboard motors 100.

[0023] The hull 200 is a portion of the boat 10 for occupants to ride. The hull 200 includes a hull main body 202 including a living space 204, a pilot seat 240 in the living space 204, and an operating device 250 near the pilot seat 240. The operating device 250 steers the boat and includes, e.g., a steering wheel 252, a shift/throttle lever 254, a joystick 255, a monitor 256, and an input device 258. The hull 200 includes a partition wall 220 to partition the rear end of the living space 204 and a transom 210 positioned at the rear end of the hull 200. In the front-rear direction, a space 206 is provided between the transom 210 and the partition wall 220.

[0024] FIG. 2 is a side view schematically illustrating a configuration of the outboard motor 100. The outboard motor 100 in the reference attitude will be described below unless otherwise specified. The reference attitude is an attitude in which the rotation axis Ac of the crank shaft 124, which will be described below, extends in the upper-lower direction, and the rotation axis Ap of the propeller shaft 137, which will be described below, extends in the front-rear direction. The front-rear direction, the left-right direction, and the upper-lower direction are respectively defined based on the outboard motor 100 in the reference attitude. The outboard motor 100 is an example of the boat propulsion device.

[0025] The outboard motor 100 generates thrust to propel the boat 10. The outboard motor 100 is attached to the transom 210 at a rear portion of the hull 200. The outboard motor 100 includes an outboard motor main body 110 and a suspension device 150.

[0026] The outboard motor main body 110 includes a cowl 112, a casing 116, an engine 120, a transmission mechanism 130, a propeller 111, a pump shaft 134, a water pump 140, and an oil pan 500.

[0027] The cowl 112 is a housing located on top of the outboard motor main body 110. The cowl 112 includes an upper cowl 113 defining an upper portion of the cowl 112 and a lower cowl 114 defining a lower portion of the cowl 112. The upper cowl 113 is detachably attached to the lower cowl 114.

[0028] The casing 116 is a housing located below the cowl 112 and provided in the lower portion of the outboard motor main body 110. The casing 116 includes an upper case 117 defining an upper portion of the casing 116 and a lower case 118 defining a lower portion of the casing 116. The upper case 117 accommodates at least a portion of the oil pan 500. The upper case 117 is an example of the case.

[0029] The engine 120 is a prime mover to generate power. The engine 120 includes, e.g., an internal combustion engine including a combustion chamber where fuel is burned (not shown). The engine 120 is located in a relatively upper portion of the outboard motor main body 110 and is accommodated in the cowl 112. The engine 120 includes a crank shaft 124 to convert the reciprocating motion of the piston, not shown, into rotational motion. The crank shaft 124 is arranged in an attitude in which its rotation axis Ac extends in the upper-lower direction.

[0030] The transmission mechanism 130 transmits the driving force of the engine 120 to the propeller 111. The transmission mechanism 130 includes an output shaft 132, a shift mechanism 300, a drive shaft 133, and a propeller shaft 137.

[0031] The output shaft 132 is a rod-shaped member extending in the upper-lower direction. The upper end of the output shaft 132 is mechanically connected to the lower end of the crank shaft 124 in the engine 120 and extends downward from a connection portion with the engine 120. The output shaft 132 rotates with the crank shaft 124 under the driving force of the engine 120.

[0032] The shift mechanism 300 is connected to the lower portion of the output shaft 132. The shift mechanism 300 transmits the driving force of the output shaft 132 to the drive shaft 133 and the pump shaft 134. By switching the rotating direction of the drive shaft 133, the shift mechanism 300 changes the rotating direction of the propeller shaft 137 and the propeller 111, thus switching the boat 10 between the forward and backward movement states.

[0033] The drive shaft 133 is a rod-shaped member that transmits power to the propeller shaft 137. The lower end of the drive shaft 133 includes a gear 135. The drive shaft 133 is mechanically connected to the propeller shaft 137 by meshing the gear 135 of the drive shaft 133 with the gear 138 of the propeller shaft 137, as described below. Rotation of the drive shaft 133 is transmitted to the propeller shaft 137 via the gear 135 of the drive shaft 133 and the gear 138 of the propeller shaft 137.

[0034] The propeller shaft 137 is a rod-shaped member and extends in the front-rear direction at a height relatively lower than the outboard motor main body 110. The propeller shaft 137 rotates with the propeller 111. The front end of the propeller shaft 137 is accommodated in the lower case 118, and the rear end of the propeller shaft 137 protrudes rearward from the lower case 118. The front end of the propeller shaft 137 includes a gear 138.

[0035] The propeller 111 is a rotor with a plurality of blades and is attached to the rear end of the propeller shaft 137. The propeller 111 rotates along with the rotation of the propeller shaft 137 about the rotation axis Ap. The propeller 111 generates thrust by rotating.

[0036] The pump shaft 134 extends in an upper-lower direction. The pump shaft 134 is driven by the driving power of the engine 120 transmitted by the output shaft 132 and the shift mechanism 300 to transmit power to the water pump 140.

[0037] The water pump 140 pumps cooling water to the cooling water flow path 400 in the outboard motor 100, which will be described below. The water pump 140 pumps water from outside the outboard motor 100. The water pump 140 is driven by the drive power of the engine 120 transmitted by the pump shaft 134. The water pump 140 is an example of the pump.

[0038] The oil pan 500 stores oil to be supplied to the engine 120. The oil has, e.g., a lubricating and cleaning function for the engine 120. The oil stored in the oil pan 500 is pumped by an oil pump (not shown) and circulates in the engine 120. The oil pan 500 is located higher than the water pump 140 and lower than the engine 120.

[0039] The suspension device 150 attaches the outboard motor main body 110 to the hull 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 behind the hull 200 in a state separated from each other in the left-right direction and are fixed to the transom 210 of the hull 200 by using, e.g., bolts. Each clamp bracket 152 has a cylindrical supporting portion 153 provided with a through-hole extending in the left-right direction.

[0041] The tilt shaft 154 is a rod-shaped member and is rotatably supported within the through-hole in the supporting portion 153 of the clamp bracket 152. The tilt axis At, which is the centerline of the tilt shaft 154, defines the horizontal (left-right) axis in the tilting operation of the outboard motor 100.

[0042] The swivel bracket 156 is sandwiched between the pair of clamp brackets 152 and is supported by the supporting portion 153 of the clamp brackets 152 via the tilt shaft 154 so as to be rotatable about the tilt axis At. The swivel bracket 156 is driven to rotate about the tilt axis At with respect to the clamp bracket 152 by a tilt device (not shown) that includes an actuator, such as a hydraulic cylinder, for example.

[0043] When the swivel bracket 156 rotates about the tilt axis At with respect to the clamp bracket 152, the outboard motor main body 110 supported by the swivel bracket 156 also rotates about the tilt axis At. This achieves the tilting operation of rotating the outboard motor main body 110 in the upper-lower direction with respect to the hull 200. By this tilting operation, the outboard motor 100 can change the angle of the outboard motor main body 110 about the tilt axis At in the range from the tilt-down state in which the propeller 111 is located under the water (the state in which the outboard motor 100 is in the reference attitude) to the tilt-up state in which the propeller 111 is located above the water surface. Trimming operation to adjust the attitude of the boat 10 during travel can also be performed by adjusting the angle about the tilt axis At of the outboard motor main body 110.

[0044] FIG. 3 is an explanatory view illustrating a cross-sectional configuration around the oil pan 500 in the outboard motor 100 according to the first example embodiment. As shown in FIG. 3, the outboard motor 100 includes a cooling water flow path 400, which is a flow path for cooling water in the outboard motor 100, located around the oil pan 500. In FIG. 3 and in the following figures, the arrows indicated on each flow path of the cooling water flow path 400 indicate the direction in which the cooling water flows in each flow path of the cooling water flow path 400.

[0045] The cooling water flow path 400 includes a first flow path 410 and a second flow path 420 (see FIG. 4). Further, the first flow path 410 includes an inlet flow path 411 and an outlet flow path 412.

[0046] The first flow path 410 is a flow path of cooling water primarily for cooling the engine 120. The first flow path 410 is configured such that the cooling water pumped by the water pump 140 passes between the oil pan 500 and the upper case 117, then around the engine 120, and then again between the oil pan 500 and the upper case 117. The first flow path 410 is configured such that the cooling water contacts the oil pan 500. Thus, the cooling water passing through the first flow path 410 passes around the oil pan 500, allowing heat transfer with the oil pan 500. Therefore, the cooling water passing through the first flow path 410 can cool not only the engine 120 but also the oil stored in the oil pan 500.

[0047] The inlet flow path 411 of the first flow path 410 extends from the water pump 140 and into the area around the combustion chamber in the engine 120. The inlet flow path 411 is configured such that the cooling water flows upward from the water pump 140. More specifically, in the inlet flow path 411, the cooling water is pumped from the water pump 140, flows around the oil pan 500, and flows toward the periphery of the combustion chamber of the engine 120, which is located above the cross-section shown in FIG. 3. The cooling water then passes around the engine 120 to cool the engine 120.

[0048] The outlet flow path of the first flow path 410 extends from the periphery of the combustion chamber in the engine 120 to the outside of the outboard motor 100. The outlet flow path 412 is configured such that the cooling water flows downward from the periphery of the combustion chamber in the engine 120. More specifically, in the outlet flow path 412, the cooling water is discharged from the periphery of the combustion chamber in the engine 120, which is located above the cross-section shown in FIG. 3, flows around the oil pan 500, flows downward from the lower case 118, and is discharged to the outside of the outboard motor 100. Thus, both of the cooling water before flowing into the periphery of the combustion chamber of the engine 120 and the cooling water after flowing out of the periphery of the combustion chamber of the engine 120 flow around the oil pan 500.

[0049] As shown in FIG. 3, the outboard motor 100 also includes an exhaust pipe 600, which is located adjacent to the oil pan 500 and through which exhaust gas discharged from the combustion chamber of the engine 120 flows. The exhaust pipe 600 is connected directly or indirectly to the combustion chamber of the engine 120, which is located above the cross-section shown in FIG. 3, and includes a portion located adjacent to the oil pan 500. More specifically, the exhaust pipe 600 includes a portion surrounded by the oil pan 500 when viewed in the upper-lower direction. Because the exhaust pipe 600 is positioned adjacent to the oil pan 500, the exhaust gas passing through the exhaust pipe 600 can warm the oil stored in the oil pan 500.

[0050] FIG. 4 is an explanatory view illustrating a cross-sectional configuration around the oil pan 500 in the outboard motor 100 according to the first example embodiment. FIG. 4 schematically illustrates the configuration of a different cross-section in the outboard motor 100 than the cross-section shown in FIG. 3. As shown in FIG. 4, the cooling water flow path 400 includes a second flow path 420. The second flow path 420 branches from the first flow path 410 from a location between the oil pan 500 and the upper case 117. More specifically, around the oil pan 500, the inlet flow path 411 is integral with the upper case 117. The connection position 422, which is the branching location of the first flow path 410 and the second flow path 420, is located between the oil pan 500 and the upper case 117. The first flow path 410 and the second flow path 420 branch at a height lower than the lower end of the oil pan 500. In the second flow path 420, the cooling water does not pass around the engine 120.

[0051] The outboard motor 100 further includes a valve 430 that changes at least one of the flow rate of the cooling water flowing into the first flow path 410 and the flow rate of the cooling water flowing out of the first flow path 410. The valve 430 is located outside the upper case 117 and is located in the middle of the second flow path 420. The outboard motor 100 adjusts the flow rate of the cooling water flowing into the first flow path 410 and the flow rate of the cooling water flowing into the second flow path 420 by opening and closing the valve 430. Specifically, the outboard motor 100 decreases the flow rate of cooling water flowing into the second flow path 420 and increases the flow rate of cooling water flowing into the first flow path 410 by closing the valve 430. Conversely, the outboard motor 100 increases the flow rate of cooling water flowing into the second flow path 420 and decreases the flow rate of cooling water flowing into the first flow path 410 by opening the valve 430. This allows the flow rate of the cooling water flowing into the first flow path 410 to be changed without changing the rotational speed of the engine 120. The valve 430 is an example of the flow rate regulator.

[0052] The valve 430 can be adjusted to any valve opening from 0% to 100%. This allows the cooling water pumped by the water pump 140 to flow into the first flow path 410 at any flow rate from 0% to 100%. Similarly, the cooling water pumped by the water pump 140 can be allowed to flow into the second flow path 420 at any flow rate from 0% to 100%.

[0053] FIG. 5 is a block diagram illustrating the control configuration of the outboard motor 100. The outboard motor 100 includes a first temperature sensor 441, a second temperature sensor 442, a third temperature sensor 443, and a fourth temperature sensor 444. The first temperature sensor 441 measures the temperature in the vicinity of the combustion chamber of the engine 120. The second temperature sensor 442 measures the temperature of the exhaust pipe 600 through which the exhaust gas discharged from the combustion chamber of the engine 120 flows. The third temperature sensor 443 measures the temperature of the oil to be supplied to the engine 120. The fourth temperature sensor 444 measures the temperature of the cooling water.

[0054] The outboard motor 100 further includes a controller 80. The controller 80 may include, e.g., a CPU, a multi-core CPU, and a programmable device (field programmable gate array (FPGA), programmable logic device (PLD), and the like). The controller 80 is electrically connected to each of the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, the fourth temperature sensor 444, the valve 430, and the engine 120.

[0055] FIG. 6 is a flowchart illustrating a control method of a valve 430 by a controller 80. The controller 80 changes the flow rate of the cooling water flowing into the first flow path 410 by operating the valve 430. Specifically, when the temperatures measured by the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444 are less than respective predetermined values (S110 to S140: YES), the controller 80 operates the valve 430 to set the flow rate of the cooling water flowing into the first flow path 410 to a first flow rate (S150). Conversely, when any of the temperatures measured by the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444 is equal to or above the respective predetermined values (S110: NO, S120: NO, S130: NO, or S140: NO), the controller 80 operates valve 430 to set the flow rate of the cooling water flowing into the first flow path 410 to a second flow rate that is higher than the first flow rate (S160). With the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444, the outboard motor 100 is able to monitor an engine temperature increase in a combined manner and reduce or prevent an excessive engine temperature increase.

[0056] FIG. 7 is a flowchart illustrating a control method of the engine 120 by the controller 80. In the idle state of the outboard motor 100, the controller 80 changes the rotation speed of the engine 120. Specifically, in the idle state of the outboard motor 100, when the temperatures measured by the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444 are less than the respective predetermined values (S210 to S240: YES), the controller 80 switches the rotation speed of the engine 120 to a first speed (S250). Conversely, in the idle state of the outboard motor 100, when any of the temperatures measured the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444 is equal to or above the respective predetermined values (S210: NO, S220: NO, S230: NO, or S240: NO), the controller 80 switches the rotation speed of the engine 120 to a second speed, which is lower than the first speed (S260). With the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444, the outboard motor 100 is able to monitor the load on the engine in a combined manner and reduce or prevent a deterioration in the fuel efficiency of the outboard motor 100.

[0057] The above predetermined values may be different from each other for the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444. With respect to the above predetermined values, the value that serves as the basis to switch the flow rate of the cooling water flowing into the first flow path 410 and the value that serves as the basis to switch the rotation speed of the engine 120 may be different from each other.

[0058] Next, the performance evaluation of the outboard motor 100 is described. The engine warm-up speeds were measured for outboard motors with different cooling water flow path configurations. A temperature sensor was placed near the combustion chamber of the engine, and the temperature near the combustion chamber of the engine was measured for a certain time after the engine was started.

[0059] FIG. 8 is an explanatory view illustrating the results of the performance evaluations. The vertical axis in FIG. 8 shows the temperature ( C.) in the vicinity of the combustion chamber of the engine in the outboard motor, and the horizontal axis in FIG. 8 shows the elapsed time from engine start of the outboard motor. The solid line in FIG. 8 shows the temperature change in the vicinity of the combustion chamber of the engine when the engine speed is increased to a high speed (twice the number of rotation at low speed as described below) for the outboard motor 100 of the first example embodiment. The dashed line in FIG. 8 shows the temperature change in the vicinity of the combustion chamber of the engine when the engine speed is set to a low speed for the outboard motor 100 of the first example embodiment. The dotted line in FIG. 8 shows the temperature change in the vicinity of the combustion chamber of the engine when the engine speed is set to the low speed for the outboard motor of the conventional configuration. The outboard motor of the conventional configuration means, more specifically, an outboard motor without the second flow path 420 in the first example embodiment, and in such an outboard motor, the flow rate of the cooling water flowing into the first flow path 410 is constant regardless of the engine temperature.

[0060] As shown in FIG. 8, the engine warm-up speed in the outboard motor 100 of the first example embodiment is higher than the engine warm-up speed in the conventional outboard motor. In addition, the engine warm-up speed in the outboard motor 100 of the first example embodiment was further improved by increasing the engine rotation speed. From these results, it was confirmed that the outboard motor 100 of the first example embodiment improves the engine warm-up speed.

[0061] FIG. 9 is an explanatory view illustrating a cross-sectional configuration around the oil pan 500 in an outboard motor 100a according to a second example embodiment. Hereinafter, the same components of the outboard motor 100a of the second example embodiment as those of the outboard motor 100 of the first example embodiment described above are designated by the same symbols, and the description of these components is omitted as appropriate. In the outboard motor 100a of the second example embodiment, the configuration of the second flow path and the valve is different from that of the outboard motor 100 of the first example embodiment.

[0062] The valve 430a in the outboard motor 100a is a three-way valve and is located inside the upper case 117. The second flow path 420a extends downward in the outboard motor 100a from the connection position 422 with the valve 430a. The outlet of the second flow path 420a is located at a lower portion of the outboard motor 100a, which is located below the cross-section shown in FIG. 9. With this configuration, the outboard motor 100a of the second example embodiment can reduce or prevent a deterioration of the valve 430a because the valve 430a is located inside the upper case 117.

[0063] FIG. 10 is an explanatory view illustrating a cross-sectional configuration around the oil pan 500 in an outboard motor 100b according to a third example embodiment. In the following, the same components of the outboard motor 100b of the third example embodiment as those of the outboard motor 100 of the first example embodiment are designated by the same symbols, and the description of these components is omitted as appropriate. In the outboard motor 100b of the third example embodiment, the configuration of the second flow path and the valve is different from that of the outboard motor 100 of the first example embodiment.

[0064] The valve 430b in the outboard motor 100b is a three-way valve and is located inside the upper case 117. The second flow path 420b extends upward in the outboard motor 100b from the connection position 422 with the valve 430b. The second flow path 420b is configured such that the cooling water passes around the ignition plug in the combustion chamber in the engine 120, which is located above the cross-section shown in FIG. 10. The ignition plug is an example of the device to be cooled. With this configuration, the outboard motor 100b of the third example embodiment can supply sufficient cooling water to the device to be cooled, such as the ignition plug in the third example embodiment, even when the engine temperature is low.

[0065] The techniques disclosed herein are not limited to the above-described example embodiments and may be modified in various ways without departing from the gist of the present invention, including the following modifications.

[0066] The configuration of the boat 10 and the outboard motor 100 of the example embodiments are only examples and may be variously modified. For example, in the above example embodiments, the outboard motor 100 is shown as an example of the boat propulsion device, but it can be an inboard motor or a jet propulsion system, for example.

[0067] In the above example embodiments, the outboard motor 100 is provided with only the engine 120 as a drive source, but the boat propulsion device may be a hybrid type equipped with a motor in addition to the engine.

[0068] In the above example embodiments, the outboard motor 100 is provided with the first temperature sensor 441, the second temperature sensor 442, the third temperature sensor 443, and the fourth temperature sensor 444, but the outboard motor may not be provided with at least one of these temperature sensors or may have another temperature sensor.

[0069] In the above example embodiments, the outboard motor 100 is provided with the controller 80, but the outboard motor need not necessarily be provided with a controller.

[0070] In the above example embodiments, the first flow path 410 and the second flow path 420 branch at a height lower than the lower end of the oil pan 500, but the branching location is not necessarily limited thereto.

[0071] In the above example embodiments, the valves 430, 430a, and 430b are provided as the flow path regulator, but the flow path regulator does not necessarily need to be a valve.

[0072] In the above example embodiments, the valve 430 is adjusted to any valve opening from 0% to 100%, but the range is not necessarily limited thereto.

[0073] Although the above example embodiments describe the outboard motor 100 and the boat 10 provided with the outboard motor 100, the technologies disclosed herein are equally applicable to movable bodies such as, e.g., vehicles and motorcycles.

[0074] 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.