BOAT AND CONTROL METHOD FOR BOAT SYSTEM

Abstract

A boat includes a first propulsion device attached to a rear portion of a boat body to generate a propulsion force along a displaceable first axis, a second propulsion device attached to the rear portion of the boat body to generate a propulsion force along a displaceable second axis, a manual operator to indicate a movement direction of the boat body, and a controller configured or programmed to set the first and second propulsion devices to a first axial attitude in which the first and second axes intersect each other rearward of the boat body when an indicated direction is within a reference angle range including a straight-ahead direction of the boat body, and set the first and second propulsion devices to a second axial attitude in which parallelism between the first and second axes is higher than the first axial attitude when the indicated direction exceeds the reference angle range.

Claims

1. A boat comprising: a boat body; a first propulsion device attached to a port side of a rear portion of the boat body to generate a propulsion force along a first axis that is displaceable; a second propulsion device attached to a starboard side of the rear portion of the boat body to generate a propulsion force along a second axis that is displaceable; a manual operator to instruct a movement direction of the boat body; and a controller configured or programmed to: set the first propulsion device and the second propulsion device to a first axial attitude in which the first axis and the second axis intersect each other rearward of the boat body when an indicated direction instructed by the manual operator is within a reference angle range including the straight-ahead direction of the boat body; and set the first propulsion device and the second propulsion device to a second axial attitude in which parallelism between the first axis and the second axis is higher than that in the first axial attitude when the indicated direction exceeds the reference angle range.

2. The boat according to claim 1, wherein the controller is configured or programmed to displace the first axis and the second axis in response to a change in the indicated direction when the indicated direction is within the reference angle range.

3. The boat according to claim 1, wherein the controller is configured or programmed to maintain an intersection angle between the first axis and the second axis at a certain angle regardless of a change in the indicated direction when the indicated direction is within the reference angle range.

4. The boat according to claim 1, wherein the controller is configured or programmed to displace the first axis and the second axis in response to a change in the indicated direction when the indicated direction exceeds the reference angle range.

5. The boat according to claim 1, wherein the controller is configured or programmed to increase the parallelism between the first axis and the second axis step-by-step or continuously as an excess angle of the indicated direction exceeding the reference angle range increases when the indicated direction exceeds the reference angle range.

6. The boat according to claim 1, wherein the second axial attitude includes an attitude in which the first axis and the second axis are parallel or approximately parallel.

7. The boat according to claim 1, wherein the controller is configured or programmed to: selectively execute a first mode to set the first propulsion device and the second propulsion device to the first axial attitude when the indicated direction is within the reference angle range, and a second mode to set the first propulsion device and the second propulsion device to the second axial attitude regardless of whether the indicated direction is within the reference angle range.

8. The boat according to claim 1, further comprising: a pair of guides located at the rear portion of the boat body and outside both the first propulsion device and the second propulsion device in a left-right direction of the boat body; wherein the pair of guides are movable to a first guide attitude that extend rearwardly and toward a longitudinal center axis of the boat body.

9. The boat according to claim 8, wherein the pair of guides are movable between the first guide attitude and a second guide attitude having a lower water guiding function than the first guide attitude; and the controller is configured or programmed to: set the pair of guides to the first guide attitude when the indicated direction is within the reference angle range; and set the pair of guides to the second guide attitude when the indicated direction exceeds the reference angle range.

10. The boat according to claim 1, further comprising: a speed sensor to measure a movement speed of the boat; wherein the controller is configured or programmed to: set the first propulsion device and the second propulsion device to the first axial direction when the indicated direction is within the reference angle range and the speed measured by the speed sensor is equal to or greater than a reference speed; and set the first boat propulsion device and the second boat propulsion device to the second axial attitude when the indicated direction is within the reference angle range and the speed measured by the speed sensor is less than the reference speed.

11. The boat according to claim 10, wherein the controller is configured or programmed to: increase the parallelism between the first axis and the second axis step-by-step or continuously as the speed measured by the speed sensor decreases when the indicated direction is within the reference angle range and the speed measured by the speed sensor is less than the reference speed.

12. The boat according to claim 1, wherein the controller is configured or programmed to change an intersection angle between the first axis and the second axis in response to an instruction from a portable terminal operated by a user when the indicated direction is within the reference angle range.

13. The boat according to claim 1, wherein the controller is configured or programmed to change a trim angle of at least one of the first axis or the second axis in response to an instruction from a portable terminal operated by a user when the indicated direction is within the reference angle range.

14. A control method for a boat system including a first propulsion device attached to a port side of a rear portion of a boat body to generate a propulsion force along a first axis, a second propulsion device attached to a starboard side of the rear portion of the boat body to generate a propulsion force along a second axis, and a manual operator to instruct the movement direction of the boat body, the method comprising: setting the first propulsion device and the second propulsion device to a first axial attitude in which the first axis and the second axis intersect each other rearward of the boat body when the indicated direction by the manual operator is within a reference angle range including a straight-ahead direction of the boat body; and setting the first propulsion device and the second propulsion device to a second axial attitude in which parallelism between the first axis and the second axis is higher than that in the first axial attitude when the indicated direction exceeds the reference angle range.

15. A boat comprising: a boat body; a first wake generator attached to a port side of a rear portion of the boat body to generate a flow of water along a first axis that is displaceable; a second wake generator attached to a starboard side of the rear portion of the boat body to generate a flow of water along a second axis that is displaceable; a manual operator to instruct a movement direction of the boat body; and a controller configured or programmed to: set the first wake generator and the second wake generator to a first axial attitude in which the first axis and the second axis intersect each other rearward of the boat body when an indicated direction instructed by the manual operator is within a reference angle range including a straight-ahead direction of the boat body; and set the first wake generator and the second wake generator to a third axial attitude that satisfies at least one condition that, compared to the first axial attitude, the parallelism between the first axis and the second axis is higher, or a force of a water flow is weaker when the indicated direction exceeds the reference angle range.

16. The boat according to claim 15, wherein at least one of the first wake generator or the second wake generator includes a guide that extends in a rearward direction and toward a longitudinal center axis of the boat body; in the first axial attitude, the guide is in an extended position protruding from the boat body; and in the third axial attitude, the guide is in a retracted position and protrudes from the boat body less than in the extended position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 is a side view that shows a configuration of a jet boat according to an example embodiment of the present invention.

[0014] FIG. 2 is a top view that shows the configuration of the jet boat.

[0015] FIG. 3 is a cross-sectional side view of the jet boat.

[0016] FIG. 4 is a bottom view that shows the configuration of the jet boat.

[0017] FIG. 5 is an explanatory view that shows a peripheral configuration of a guide.

[0018] FIG. 6 is a block diagram that shows an electrical configuration of the jet boat.

[0019] FIG. 7 is an explanatory view that shows first and second propulsion devices in a toe-in attitude.

[0020] FIG. 8 is an explanatory view that shows a status of the propulsion devices and the guide when a steering angle is in a straight-ahead position.

[0021] FIG. 9 is an explanatory view that shows the status of the propulsion devices and the guide when the steering angle is between the straight-ahead position and the right-side reference angle.

[0022] FIG. 10 is an explanatory view showing the status of the propulsion devices and the guide when the steering angle is between the straight-ahead position and the left-side reference angle.

[0023] FIG. 11 is an explanatory view showing the status of the propulsion devices and the guide when the steering angle exceeds the right-side reference angle.

[0024] FIG. 12 is an explanatory view showing the status of the propulsion devices and the guide when the steering angle exceeds the left-side reference angle.

[0025] FIG. 13 is a flowchart showing a control process of the propulsion devices and the guide.

[0026] FIG. 14 is a graph showing a relationship between the steering angle and a boat movement speed.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0027] FIG. 1 is a side view that shows the configuration of a jet boat 10 according to an example embodiment of the present invention, and FIG. 2 is a top view that shows the configuration of the jet boat 10. FIGS. 1 and 2 include arrows representing each direction with respect to the position of the jet boat 10. More specifically, each figure shows arrows representing front (FRONT), rear (REAR), left (LEFT), right (RIGHT), upper (UPPER), and lower (LOWER) directions. The front-rear, left-right, and upper-lower (vertical) directions are perpendicular to each other. The jet boat 10 is one example of a boat according to an example embodiment of the present invention.

[0028] The jet boat 10 includes a boat body 200, a first propulsion device 100A, and a second propulsion device 100B. In this example embodiment, the jet boat 10 includes a pair of propulsion devices 100A, 100B, but the jet boat 10 may include three or more propulsion devices. The first propulsion device 100A is an example of a first wake generator, and the second propulsion device 100B is an example of a second wake generator.

[0029] The boat body 200 includes a deck 201 and a hull 202. The hull 202 is arranged below the deck 201. A steering seat 220 is arranged on the deck 201. The first propulsion device 100A and the second propulsion device 100B are attached to the boat body 200. The first propulsion device 100A is attached to the port side of the rear portion of the boat body 200. The second propulsion device 100B is attached to the starboard side of the rear portion of the boat body 200. The first propulsion device 100A and the second propulsion device 100B are, for example, jet propulsion devices. The first propulsion device 100A and the second propulsion device 100B are arranged in a line-symmetrical position with respect to the center axis O, which passes through the center in the left-right direction of the boat body 200 and extends in the front-rear direction. The center axis O is an example of the longitudinal center axis of the boat body.

[0030] FIG. 3 is a cross-sectional side view of the jet boat 10. FIG. 3 shows a cross-section of a portion of the first propulsion device 100A. As shown in FIG. 3, the first propulsion device 100A is accommodated in the boat body 200. The first propulsion device 100A includes a first engine 104A, a first jet pump 105A, a first nozzle deflector 106A, and a first reverse gate 107A. The first engine 104A is connected to the first jet pump 105A. The first jet pump 105A is driven by the first engine 104A to suck in and jet out water around the boat body 200. Thus, the first jet pump 105A generates a propulsion force to move the boat body 200.

[0031] The first jet pump 105A includes a drive shaft 121, an impeller 122, and a pump housing 123. The drive shaft 121 is connected to the output shaft 125 of the first engine 104A via a coupling 124. The impeller 122 is connected to the drive shaft 121. The impeller 122 is disposed within the pump housing 123. The impeller 122 rotates together with the drive shaft 121 to suck in water from the water intake port 126. The impeller 122 jets out the sucked-in water to the rear from the jet outlet of the pump housing 123.

[0032] The first nozzle deflector 106A is arranged behind the first jet pump 105A. The first nozzle deflector 106A is able to swing in the left-right direction and the upper-lower direction. The first nozzle deflector 106A changes the jet stream direction of the water from the first jet pump 105A in the left-right direction and the upper-lower direction. The first reverse gate 107A is arranged behind the first nozzle deflector 106A. The first reverse gate 107A is switchable between a forward movement position and a backward movement position. By switching the first reverse gate 107A between the forward movement position and the backward movement position, the jet stream direction from the first jet pump 105A is changed. This switches the jet boat 10 between moving forward and moving backward.

[0033] The second propulsion device 100B has the same configuration as the first propulsion device 100A. As shown in FIG. 2, the second propulsion device 100B includes a second engine 104B, a second jet pump 105B, a second nozzle deflector 106B, and a second reverse gate 107B. The second engine 104B, the second jet pump 105B, the second nozzle deflector 106B, and the second reverse gate 107B are similar to the first engine 104A, the first jet pump 105A, the first nozzle deflector 106A, and the first reverse gate 107A, so a detailed explanation is omitted.

[0034] FIG. 4 is a bottom view that shows the configuration of the jet boat 10. As shown in FIG. 4, the jet boat 10 further includes a first guide 300A and a second guide 300B. The first guide 300A and the second guide 300B are attached to the lower surface of the rear portion (transom step 216) of the boat body 200. The first guide 300A and the second guide 300B are arranged on the left and right sides of the first propulsion device 100A and the second propulsion device 100B, respectively. The first guide 300A is arranged to the left of the first propulsion device 100A, more specifically, the first nozzle deflector 106A. The second guide 300B is arranged to the right of the second propulsion device 100B, more specifically, the second nozzle deflector 106B. The first guide 300A and the second guide 300B are arranged in a line-symmetrical position with respect to the center axis O of the boat body 200. The first guide 300A is another example of the first wake generator, and the second guide 300B is another example of the second wake generator.

[0035] The first guide 300A and the second guide 300B each extend in a rearward direction and toward the center axis O of the boat body 200. The first guide 300A is a plate-like member that extends along a rearward oblique right direction so that the rear end thereof extends toward the central axis O. The second guide 300B is a plate-like member that extends along a rearward oblique left direction so that the rear end thereof extends toward the central axis O. The guide axis along the direction of the water guided by the first guide 300A and the guide axis along the direction of the water guided by the second guide 300B intersect on the central axis O rearward of the boat body 200. In the following, the attitude in which the guide axis of the first guide 300A and the guide axis of the second guide 300B intersect rearward of the boat body 200 is referred to as the guide-enabled attitude. The guide-enabled attitude is an example of the first guide attitude and the first axial attitude. The guide axis of the first guide 300A is an example of the first axis, and the guide axis of the second guide 300B is an example of the second axis.

[0036] FIG. 5 is an explanatory view that shows the peripheral configuration of the first guide 300A. The first guide 300A is provided on the boat body 200 in a manner that allows it to be displaced between a retracted position and an extended position. The retracted position is a position in which the first guide 300A is accommodated within the boat body 200. The extended position is a position in which the first guide 300A protrudes downward from the boat body 200 (see FIG. 4). Specifically, the jet boat 10 includes a first guide actuator 310A and an arm 312. The first guide 300A is supported by the boat body 200 in a displaceable manner about a rotation shaft 314. The first guide actuator 310A displaces the first guide 300A between a retracted position (indicated by the dotted line in FIG. 5) and an extended position (indicated by the solid line in FIG. 5) by controlling the arm 312. Similarly, the second guide 300B is displaced between a retracted position and an extended position by the control of the second guide actuator 310B.

[0037] FIG. 6 is a block diagram that shows the electrical configuration of the jet boat 10. As shown in FIG. 6, the jet boat 10 includes a controller 400. The controller 400 includes a processor such as a CPU and memory such as RAM and ROM. The controller 400 is configured or programmed to control the jet boat 10.

[0038] The jet boat 10 includes a first steering actuator 131A and a first shift actuator 132A. The controller 400 is communicatively connected to the first engine 104A, the first steering actuator 131A, and the first shift actuator 132A.

[0039] The first steering actuator 131A is connected to the first nozzle deflector 106A of the first propulsion device 100A. The first steering actuator 131A changes the first jet stream direction D1, which is the direction of the water jet from the first nozzle deflector 106A. FIG. 7 is an explanatory view that shows the first propulsion device 100A and the second propulsion device 100B in a toe-in attitude. As shown in FIG. 7, the first jet stream direction D1 extends in the rearward direction along the axis M1 of the first nozzle deflector 106A. The first jet stream direction D1 can be expressed as the nozzle angle x of the first nozzle deflector 106A. The nozzle angle x is the angle formed by the direct rearward direction in the front-rear direction M0 and the first jet stream direction D1. The nozzle angle x is the angle of the axis M1 of the first nozzle deflector 106A extending rearward from the first nozzle deflector 106A relative to the front-rear direction M0 of the jet boat 10. The first steering actuator 131A changes the nozzle angle x of the first jet stream direction D1 to which the first propulsion device 100A pushes out water. The first steering actuator 131A includes, e.g., an electric motor. The first steering actuator 131A may be another type of actuator such as a hydraulic cylinder. The axis M1 is an example of the first axis.

[0040] The first shift actuator 132A is connected to the first reverse gate 107A of the first propulsion device 100A. The first shift actuator 132A switches the position of the first reverse gate 107A between a forward movement position and a backward movement position. The first shift actuator 132A includes, e.g., an electric motor. The first shift actuator 132A may be another type of actuator, such as a hydraulic cylinder.

[0041] The jet boat 10 includes a second steering actuator 131B and a second shift actuator 132B. The controller 400 is communicatively connected to the second engine 104B, the second steering actuator 131B, and the second shift actuator 132B. The second steering actuator 131B changes the second jet stream direction D2, which is the direction of the water jet from the second nozzle deflector 106B. As shown in FIG. 7, the second jet stream direction D2 extends in the rearward direction along the axis M2 of the second nozzle deflector 106B. The second jet stream direction D2 can be expressed as the nozzle angle of the second nozzle deflector 106B. The nozzle angle is the angle formed by the direct rearward direction in the front-rear direction M0 and the second jet stream direction D2. The nozzle angle is the angle of the axis M2 of the second nozzle deflector 106B extending rearward from the second nozzle deflector 106B relative to the front-rear direction M0 of the jet boat 10. The second steering actuator 131B changes the nozzle angle of the second jet stream direction D2 to which the second propulsion device 100B pushes out water. The second steering actuator 131B includes, e.g., an electric motor. The second steering actuator 131B may be another type of actuator such as a hydraulic cylinder. The axis M2 is an example of the second axis.

[0042] The second shift actuator 132B is connected to the second reverse gate 107B of the second propulsion device 100B. The second shift actuator 132B switches the position of the second reverse gate 107B between a forward movement position and a backward movement position. The second shift actuator 132B includes, e.g., an electric motor. The second shift actuator 132B may be another type of actuator, such as a hydraulic cylinder.

[0043] The jet boat 10 includes a steering member 214 (steering unit) and a remote controller 215 (throttle unit). The controller 400 is communicatively connected to the steering member 214 and the remote controller 215. The steering member 214 and the remote controller 215 are arranged near the steering seat 220. The steering member 214 is an example of the manual operator (steering device).

[0044] The steering member 214 is operated to steer the jet boat 10. In other words, the controller 400 controls the bow direction of the jet boat 10 in response to the operation of the steering member 214. The steering member 214 includes, e.g., a steering wheel. The steering member 214 includes a sensor 140. The sensor 140 outputs a steering signal indicating the operation direction and operation amount of the steering member 214.

[0045] The controller 400 receives the steering signal from the sensor 140. The controller 400 controls the nozzle angle x (the first jet stream direction D1) of the first propulsion device 100A by controlling the first steering actuator 131A based on the steering signal. The controller 400 controls the nozzle angle (the second jet stream direction D2) of the second propulsion device 100B by controlling the second steering actuator 131B based on the steering signal. This changes the direction of the bow of the jet boat 10 in the left-right direction.

[0046] The remote controller 215 adjusts the magnitude of the thrust of the first propulsion device 100A and the second propulsion device 100B. The remote controller 215 includes a first throttle member 215A and a second throttle member 215B. The first throttle member 215A is operated to adjust the output of the first engine 104A and to switch between forward movement and backward movement. The second throttle member 215B is operated to adjust the output of the second engine 104B and to switch between forward movement and backward movement. The first throttle member 215A includes a sensor 151 (opening sensor). The sensor 151 outputs a first throttle signal indicating the operation direction and operation amount of the first throttle member 215A. The second throttle member 215B includes a sensor 152 (opening sensor). The sensor 152 outputs a second throttle signal indicating the operation direction and operation amount of the second throttle member 215B. The first throttle member 215A and the second throttle member 215B each include a lever.

[0047] The controller 400 receives the first throttle signal and the second throttle signal. The controller 400 controls the rotation speed of the first engine 104A according to the operation amount of the first throttle member 215A indicated by the first throttle signal. The controller 400 controls the rotation speed of the second engine 104B according to the operation amount of the second throttle member 215B indicated by the second throttle signal. The controller 400 controls the first shift actuator 132A according to the operation direction of the first throttle member 215A indicated by the first throttle signal. This switches the direction of the propulsion force of the first propulsion device 100A between the forward direction and the backward direction. The controller 400 controls the second shift actuator 132B according to the operation direction of the second throttle member 215B indicated by the second throttle signal. This switches the direction of the propulsion force of the second propulsion device 100B between the forward direction and the backward direction.

[0048] As shown in FIG. 6, the jet boat 10 includes a first rotation speed sensor 133A and a second rotation speed sensor 133B. The controller 400 is communicatively connected to the first rotation speed sensor 133A and the second rotation speed sensor 133B.

[0049] The first rotation speed sensor 133A detects the rotation speed of the first engine 104A. The first rotation speed sensor 133A outputs a first rotation speed signal indicating the rotation speed of the first engine 104A to the controller 400. The second rotation speed sensor 133B detects the rotation speed of the second engine 104B. The second rotation speed sensor 133B outputs a second rotation speed signal indicating the rotation speed of the second engine 104B to the controller 400. The controller 400 detects the movement speed of the jet boat 10 from the first rotation speed signal or the second rotation speed signal. Furthermore, in addition to determining the movement speed from the first rotation speed signal and the second rotation speed signal, the controller 400 may also determine the movement speed of the jet boat 10 based on the opening of the first throttle member 215A indicated by the first throttle signal from the sensor 151 and the opening of the second throttle member 215B indicated by the second throttle signal from the sensor 152. The controller 400 may also determine the movement speed of the jet boat 10 by using a Global Positioning System (GPS), for example. The first rotation speed sensor 133A and the second rotation speed sensor 133B are examples of speed sensors.

[0050] The controller 400 is communicatively connected to the first guide actuator 310A and the second guide actuator 310B. The controller 400 controls the first guide actuator 310A and the second guide actuator 310B. The first guide actuator 310A and the second guide actuator 310B may be, e.g., electric motors, but they may be other actuators such as hydraulic cylinders.

[0051] FIGS. 8 to 12 are explanatory views showing the status of the propulsion device and the guide. Each diagram also shows the status of the steering member 214 and a graph showing the relationship between the steering angle of the steering member 214 and the nozzle angle.

[0052] The horizontal axis of the graph shows the steering angle (wheel angle) of the steering member 214. The negative side of the horizontal axis indicates the wheel angle towards the port side, and the positive side of the horizontal axis indicates the wheel angle towards the starboard side, with the origin indicating the neutral position (straight-ahead position). A larger negative value indicates that the steering member 214 was operated more towards the left, and a larger positive value indicates that the steering member 214 was operated more towards the right. The vertical axis of the graph indicates the nozzle angle. The origin indicates the status where the nozzle angle is zero, and the first jet stream direction D1 and the second jet stream direction D2 are along the front-rear direction M0. The positive side of the vertical axis indicates the magnitude of the nozzle angle to the starboard side, and the negative side of the vertical axis indicates the magnitude of the nozzle angle to the port side. A larger positive value indicates that the nozzle angle has increased to the port side, and a larger negative value indicates that the nozzle angle has increased to the starboard side. The first graph G1 shows the change in nozzle angle x of the first nozzle deflector 106A with respect to the steering angle, and the second graph G2 shows the change in nozzle angle of the second nozzle deflector 106B with respect to the steering angle. The direction indicated by the steering angle of the steering member 214 is an example of the indicated direction.

[0053] FIG. 13 is a flowchart showing a control process of the propulsion device and the guide, and FIG. 14 is a graph showing the relationship between the steering angle and the movement speed. When the jet boat 10 is activated, the controller 400 executes the control process shown in FIG. 13. The controller 400 determines whether it is set to the wake surfing mode (S110). The user can select between the normal mode and the wake surfing mode by using the manual operator provided on the steering seat 220. The wake surfing mode is a mode for wake surfing, and the jet boat 10 forms a wave W for wake surfing in the rearward direction of the boat body 200 (see FIGS. 8 to 10). The normal mode is a mode for normal operation of the jet boat 10, and the jet boat 10 does not form the wave W for wake surfing (see FIGS. 11 and 12). The wake surfing mode is an example of the first mode, and the normal mode is an example of the second mode.

[0054] Upon determining that the setting is in the wake surfing mode (S110: YES), the controller 400 determines whether the steering angle of the steering member 214 is within a reference angle range ER (S120). The reference angle range ER is narrower than the maximum possible steering angle range of the steering member 214. The reference angle range ER is the range from the port-side upper limit angle to the starboard-side upper limit angle. The port-side upper limit angle is the angle of neutral position (angle zero)+ (e.g., 50 degrees or less), and the starboard-side upper limit angle is the angle of neutral position.

[0055] Upon determining that the steering angle of the steering member 214 is within the reference angle range ER (S120: YES), the controller 400 determines whether the movement speed (boat speed) of the jet boat 10 is equal to or greater than a reference speed Va (see FIG. 14, e.g., 8 mph or less) (S130). Upon determining that the movement speed is equal to or greater than the reference speed Va (S130: YES), the controller 400 executes a toe-in attitude control (S140). The toe-in attitude control is a control that sets the first propulsion device 100A and the second propulsion device 100B in a toe-in attitude. The toe-in attitude is an attitude in which the axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B intersect rearward of the boat body 200. When the first propulsion device 100A and the second propulsion device 100B are driven in the toe-in attitude, the propulsion forces of the first jet stream direction D1 and the propulsion force of the second jet stream direction D2 intersect rearward of the boat body 200 forming the wave W for wake surfing. The toe-in attitude is an example of the first axial attitude.

[0056] In the toe-in attitude control, the controller 400 sets the first guide 300A and the second guide 300B to the extended position in the guide-enabled attitude. In the guide-enabled attitude, the water flow along the guide axis of the first guide 300A and the water flow along the guide axis of the second guide 300B intersect rearward of the boat body 200 to form the wave W for wake surfing. At this time, the propulsion forces of the first propulsion device 100A and the second propulsion device 100B, which are in the toe-in attitude, reduce or prevent splashing of water on the wave W for wake surfing.

[0057] In the toe-in attitude control, as long as the steering angle by the steering member 214 is within the reference angle range ER, while maintaining the toe-in attitude of the first propulsion device 100A and the second propulsion device 100B, the controller 400 displaces the axis M1 (nozzle angle ) of the first nozzle deflector 106A and the axis M2 (nozzle angle ) of the second nozzle deflector 106B in response to a change in the steering angle of the steering member 214. Specifically, this control is as follows.

[0058] In FIG. 8, the steering angle of the steering member 214 is in the neutral position. At this time, the first propulsion device 100A and the second propulsion device 100B are in the toe-in attitude, and the first guide 300A and the second guide 300B are in the guide-enabled attitude. Hereinafter, the angle formed by the axis M1 and the axis M2 when in the toe-in attitude is referred to as the intersection angle . The intersection point P of the axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B is located on the centerline O of the boat body 200. Therefore, the jet boat 10 forms the wave W for wake surfing in the rearward direction while traveling straight ahead. A user U can ride the wave W with a wakeboard S and perform wake surfing.

[0059] In FIG. 9, the steering angle of the steering member 214 is an angle shifted to the right rotating direction from the neutral position. In this case, the first propulsion device 100A and the second propulsion device 100B are in the toe-in attitude, and the first guide 300A and the second guide 300B are in the guide-enabled attitude. The intersection angle of the toe-in attitude is the same angle () as when traveling straight ahead (FIG. 8). The intersection point P of the axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B is located to the right of the center axis O of the boat body 200. Therefore, the jet boat 10 forms the wave W for wake surfing in the rearward direction while turning to the right. Thus, the user U can perform wake surfing.

[0060] In FIG. 10, the steering angle of the steering member 214 is an angle shifted to the left rotating direction from the neutral position. In this case, the first propulsion device 100A and the second propulsion device 100B are in the toe-in attitude, and the first guide 300A and the second guide 300B are in the guide-enabled attitude. The intersection angle of the toe-in attitude is the same angle () as when traveling straight ahead (FIG. 8). The intersection point P of the axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B is located to the left of the center axis O of the boat body 200. Therefore, the jet boat 10 forms the wave W for wake surfing in the rearward direction while turning to the left. Thus, the user U can perform wake surfing.

[0061] Upon determining that the setting is in the normal mode (S110: NO), the controller 400 executes a parallel attitude control (S150). In other words, in the normal mode, the controller 400 executes the parallel attitude control regardless of whether the steering angle is within the reference angle range ER or not. The parallel attitude control is a control that causes the first propulsion device 100A and the second propulsion device 100B to be in a parallel attitude. The parallel attitude is an attitude in which the axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B are parallel. When the first propulsion device 100A and the second propulsion device 100B are driven in the parallel attitude, the propulsion forces in the first jet stream direction D1 and the second jet stream direction D2 act in the same direction to propel the jet boat 10. At this time, the wave W for wake surfing is not formed. The parallel attitude is an example of the second axial attitude.

[0062] Upon determining that the setting is in the wake surfing mode and the steering angle of the steering member 214 has exceeded the reference angle range ER (S110: YES and S120: NO), the controller 400 executes the parallel attitude control (S150). At this time, while maintaining the first propulsion device 100A and the second propulsion device 100B in a parallel transition attitude or the parallel attitude, the controller 400 displaces the axis M1 of the first nozzle deflector 106A (nozzle angle x) and the axis M2 of the second nozzle deflector 106B (nozzle angle ) in response to a change in the steering angle by the steering member 214. The parallel transition attitude is an attitude in which the parallelism between the axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B is higher (closer to a parallel attitude) than the toe-in attitude described above. The parallel transition attitude is an example of the second axial attitude. Specifically, this control is as follows.

[0063] In FIG. 11, the steering angle of the steering member 214 exceeds the reference angle range ER by an excess angle ARB to the right rotating direction. At this time, the first propulsion device 100A and the second propulsion device 100B are in the parallel transition attitude, and the first guide 300A and the second guide 300B are both in a guide-disabled attitude in the retracted position. The axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B are tilted at a backward oblique right direction at a steering angle corresponding to the right rotation angle from the neutral position of the steering member 214. Therefore, the jet boat 10 turns smoothly to the right at a steering angle corresponding to the change in rotational position of the steering member 214. The guide-disabled attitude is an example of the second guide axial attitude and the third axial attitude.

[0064] The controller 400 increases the parallelism of the axis M1 and the axis M2 step-by-step or continuously as the above-mentioned excess angle ARB of the steering angle increases. In other words, when the steering angle of the steering member 214 exceeds the reference angle range ER, the first propulsion device 100A and the second propulsion device 100B transition from the toe-in attitude to the parallel attitude as the excess angle ARB in the right rotating direction increases. The gradual transition from the toe-in attitude to the parallel attitude reduces the effect of the attitude displacement of the first propulsion device 100A and the second propulsion device 100B on the smooth right turning of the jet boat 10.

[0065] In FIG. 12, the steering angle of the steering member 214 exceeds the reference angle range ER by an excess angle ARA to the left rotating direction. At this time, the first propulsion device 100A and the second propulsion device 100B are in the parallel transition attitude, and the first guide 300A and the second guide 300B are both in the guide-disabled attitude in the retracted position. The axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B are tilted in a backward oblique left direction at a steering angle corresponding to the left rotation angle from the neutral position of the steering member 214. Therefore, the jet boat 10 turns smoothly to the left at a steering angle corresponding to the change in rotational position of the steering member 214.

[0066] The controller 400 increases the parallelism of the axis M1 and the axis M2 step-by-step or continuously as the above-mentioned excess angle ARA of the steering angle increases. In other words, when the steering angle of the steering member 214 exceeds the reference angle range ER, the first propulsion device 100A and the second propulsion device 100B transition from the toe-in attitude to the parallel attitude as the excess angle ARA in the left rotating direction increases. The gradual transition from the toe-in attitude to the parallel attitude inhibits the attitude displacement of the first propulsion device 100A and the second propulsion device 100B from interfering with the smooth left turning of the jet boat 10.

[0067] Upon determining that the steering angle of the steering member 214 is within the reference angle range ER and the movement speed of the jet boat 10 is less than the reference speed Va (S120: YES and S130: NO), the controller 400 executes the parallel attitude control (S150). While maintaining the first propulsion device 100A and the second propulsion device 100B in a parallel transition attitude or a parallel attitude, the controller 400 displaces the axis M1 (nozzle angle ) of the first nozzle deflector 106A and the axis M2 (nozzle angle ) of the second nozzle deflector 106B in response to a change in the steering angle of the steering member 214. As shown in FIG. 14, the controller 400 causes the first propulsion device 100A and the second propulsion device 100B to transition from the toe-in attitude to the parallel attitude as the movement speed of the jet boat 10 decreases. In addition, the controller 400 causes the first guide 300A and the second guide 300B to transition from the guide-enabled attitude to the guide-disabled attitude. For example, if the user U falls off the wakeboard S, the operator of the jet boat 10 can slow down the jet boat 10 to automatically move the first propulsion device 100A and the second propulsion device 100B to the parallel attitude, and automatically move the first guide 300A and the second guide 300B to the guide-disabled attitude. This improves the maneuverability (turning ability) of the jet boat 10 to rescue the user U more quickly.

[0068] The technologies disclosed herein are not limited to the above-described example embodiments and may be modified in various forms without departing from the gist of the present invention, including the following modifications.

[0069] The configurations of the jet boats 10 in the above example embodiments are merely examples and can be modified in various ways. For example, in the above example embodiments, the first nozzle deflector 106A and the second nozzle deflector 106B may be able to swing in the left-right direction, but not in the upper-lower direction. In the above example embodiments, the jet boat 10 may not be provided with the first guide 300A and the second guide 300B. In the above example embodiments, the first nozzle deflector 106A and the second nozzle deflector 106B may always be in the parallel attitude. In this case, the controller 400 sets the first guide 300A and the second guide 300B to the guide-enabled attitude when the steering angle of the steering member 214 is within the reference angle range ER and sets them to the guide-disabled attitude when the steering angle exceeds the reference angle range ER.

[0070] In the above example embodiments, the guide-disabled attitude was used as an example of the second guide axial attitude, but, for example, the first guide 300A and the second guide 300B may be in the extended position and the parallelism of the guide axis of the first guide 300A and the guide axis of the second guide 300B may be higher than the guide-enabled attitude described above.

[0071] In the above example embodiments, the intersection angle was maintained constant during the toe-in attitude control, but, for example, the intersection angle may be changed in accordance with the steering angle.

[0072] In the above example embodiments, the controller 400 may be configured or programmed to change the intersection angle between the axis M1 of the first nozzle deflector 106A and the axis M2 of the second nozzle deflector 106B in response to an instruction from a portable terminal (not shown) operated by the user U during the execution of the toe-in attitude control. The controller 400 may also be configured or programmed to individually change the tilt angle of at least one of the axis M1 of the first nozzle deflector 106A or the axis M2 of the second nozzle deflector 106B in response to an instruction from a portable terminal operated by the user U during the execution of the toe-in attitude control. In the above example embodiments, the controller 400 may be configured or programmed to change the upper-lower direction angle (trim angle) of at least one of the axis M1 of the first nozzle deflector 106A or the axis M2 of the second nozzle deflector 106B in response to an instruction from a portable terminal operated by the user U during the execution of the toe-in attitude control. With this kind of configuration, the user U can change the wave pattern of the wave W for wake surfing to suit his/her preferences while wake surfing.

[0073] In the above example embodiments, the jet boat 10 equipped with the jet propulsion devices is exemplified as the boat, but the boat is not limited to this and can also be a water jet propulsion boat, a boat equipped with an inboard motor, an inboard/outboard motor or an outboard motor, among others. The drive source of the propulsion device is not limited to an engine, but can also be an electric motor and the like.

[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.