MARINE VESSEL AND CONTROL DEVICE THEREFOR

Abstract

A control device for a marine vessel includes a hull, a pair of water resistance bodies, and a controller. The pair of water resistance bodies are provided on the hull, one on a left side and one on a right side of the hull, each independently movable between a first position in which a resistance received from water in a predetermined direction is adjustable to a first magnitude, and a second position in which a resistance is adjustable to zero or to a second magnitude smaller than the first magnitude. The controller is configured or programmed to acquire wind speed, acquire tidal current speed, and control is configured or programmed to control the pair of water resistance bodies based on the wind speed and the tidal current speed.

Claims

1. A control device for a marine vessel, the control device comprising: a hull; a pair of water resistance bodies on the hull, one on a left side of the hull and one on a right side of the hull, each independently movable between a first position in which a resistance received from water in a predetermined direction is adjustable to a first magnitude, and a second position in which a resistance is adjustable to zero or to a second magnitude smaller than the first magnitude; and a controller configured or programmed to: acquire wind speed; acquire tidal current speed; and control the pair of water resistance bodies based on the wind speed and the tidal current speed.

2. The control device according to claim 1, wherein the controller is configured or programmed to set the pair of water resistance bodies to the first position when a predetermined condition is satisfied in which the wind speed exceeds a predetermined speed, or the wind speed is greater than a value derived from the tidal current speed.

3. The control device according to claim 2, wherein the controller is configured or programmed to set the pair of water resistance bodies to the second position when the predetermined condition is not satisfied.

4. The control device according to claim 2, wherein the predetermined direction corresponds to a front-rear direction of the hull; and the controller is configured or programmed to: acquire a hull orientation; acquire a tidal current direction; and set one of the pair of water resistance bodies to the first position and another one of the pair of water resistance bodies to the second position when an angular deviation between the hull orientation and the tidal current direction exceeds a predetermined angle, regardless of whether the predetermined condition is satisfied.

5. The control device according to claim 4, wherein one of the pair of water resistance bodies set to the first position when the angular deviation exceeds the predetermined angle is configured to generate a rotational moment in a direction to correct the angular deviation.

6. The control device according to claim 4, wherein the pair of water resistance bodies are each configured to pivot about a pivot shaft parallel to an up-down direction; the first position is a pivoted position where the pair of water resistance bodies are perpendicular to the front-rear direction of the hull; and the second position is a pivoted position where the water resistance bodies are parallel to the front-rear direction of the hull.

7. The control device according to claim 4, further comprising: a pair of global navigation satellite system sensors to detect the hull orientation; and a tidal current sensor to detect the tidal current direction.

8. The control device according to claim 1, wherein each of the pair of water resistance bodies is plate-shaped.

9. The control device according to claim 1, further comprising: a pair of water resistance assemblies each including: a rotary motor to move one of the pair of water resistance bodies between the first position and the second position; and a lifting motor to move one of the pair of water resistance bodies up and down relative to the hull.

10. The control device according to claim 1, further comprising: a wind speed sensor to detect the wind speed; and a tidal current sensor to detect the tidal current speed.

11. A marine vessel comprising: the control device according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIGS. 1A and 1B are schematic top views of a marine vessel.

[0010] FIGS. 2A to 2D are schematic right-side views of the marine vessel.

[0011] FIG. 3 is a block diagram of a marine propulsion system.

[0012] FIG. 4 is a flowchart of a drift fishing mode process.

[0013] FIGS. 5A and 5B are schematic diagrams illustrating an example of a control of water resistance bodies on a hull.

[0014] FIGS. 6A to 6C are schematic diagrams illustrating an example of a transition of the hull's movement when the wind direction and tidal current direction are not parallel to each other.

[0015] FIGS. 7A and 7B are schematic diagrams illustrating modifications of the water resistance bodies.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0016] Example embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] FIGS. 1A and 1B are schematic top views of a marine vessel 1 that uses a control device according to an example embodiment of the present invention. The marine vessel 1 includes a hull 2. FIGS. 1A and 1B illustrate the states in which water resistance bodies 93 (e.g., resistance plates described in more detail below) mounted to the hull 2 are located in a second position and a first position, respectively.

[0018] A centerline C of the hull 2 extends through the center of the stern and the tip of the bow. The centerline C also extends through the center of gravity G (turning center) of the marine vessel 1. The front-rear direction is parallel to the centerline C (hereinafter parallel includes both parallel and substantially parallel). The forward direction is a direction along the centerline C in FIG. 1A from the stern toward the bow. The backward direction is a direction along the centerline C in FIG. 1A from the bow toward the stern. As used herein, the terms left and right are defined based on the perspective when the hull 2 is viewed from the rear. The up-down direction is a direction perpendicular to both the front-rear direction and the left-right direction (hereinafter perpendicular includes both perpendicular and substantially perpendicular).

[0019] The marine vessel 1 includes a steerable outboard motor 4 and a steerable trolling motor 5 as propulsion devices to propel the hull 2. The outboard motor 4 is located at the stern, while the trolling motor 5 is located at the bow. The outboard motor 4 and the trolling motor 5 may serve as the primary and auxiliary propulsion devices of the marine vessel 1, respectively.

[0020] The marine vessel 1 further includes a steering wheel 11 mainly used to steer, a remote control unit 12 mainly used to adjust the output of the outboard motor 4, and a joystick 13 mainly used to both steer and adjust the output of the outboard motor 4 (see FIG. 3). The remote control unit 12 includes two throttle levers (not illustrated) that are operated to adjust the engine output of the outboard motor 4 and to switch between forward and reverse travel. Each throttle lever is operable from a neutral position in both the forward and reverse directions.

[0021] As illustrated in FIG. 1A, the outboard motor 4 includes an outboard motor body 20 and a propeller 21. The outboard motor body 20 is attached to the stern via an attachment mechanism, specifically to a swivel bracket (not illustrated) of the attachment mechanism so as to be pivotable about a steering axis center K. The steering angle of the outboard motor 4 changes as the outboard motor body 20 pivots about the steering axis center K. The trolling motor 5 is configured to provide a propulsive force to the hull 2 in any direction around a rotation axis J2. For example, the trolling motor 5 may be electrically powered.

[0022] A pair of left and right water resistance assemblies 90L and 90R are arranged at the stern. The water resistance assemblies 90L and 90R each include a rotary motor 91, a lifting motor 92, a water resistance body 93 (e.g., a resistance plate), a fixed body 94, and a movable body 95. The water resistance assemblies 90L and 90R are arranged and configured symmetrically with respect to the centerline C. The water resistance assemblies 90L and 90R can be driven independently. Since their basic configurations are the same, the configuration of the water resistance assembly 90L will be described as a representative example.

[0023] The fixed body 94 is fixed to the stern, and the movable body 95 is movable in the up-down direction relative to the fixed body 94 (at least between a raised position and a lowered position). The water resistance body 93 is pivotable about the rotation axis J1 and is movable to the second position illustrated in FIG. 1A and to the first position illustrated in FIG. 1B. The rotation axis J1 is the axis center of a pivot shaft that is parallel to the up-down direction.

[0024] FIGS. 2A to 2D are schematic right-side views of the marine vessel 1.

[0025] FIGS. 2A and 2B illustrate a state where the water resistance body 93 is in the second position, while FIGS. 2C and 2D illustrate a state where the water resistance body 93 is in the first position. FIGS. 2B and 2D illustrate a state where the movable body 95 is in the raised position, while FIGS. 2A and 2C illustrate a state where the movable body 95 is in the lowered position in a drift fishing mode other than during normal sailing.

[0026] The lifting motor 92 drives the movable body 95 to move it up and down relative to the fixed body 94. The rotary motor 91 causes the water resistance body 93 to pivot about the rotational axis J1. The lifting motor 92 and the rotary motor 91 are automatically controlled by a controller 70 (described below) and can also be manually operated using a water resistance switch (SW) 30 (see FIG. 3).

[0027] The first position is a position where the water resistance body 93 is perpendicular to the front-rear direction. In this position, the water resistance body 93 defines an angle of 90 (hereinafter, 90 includes both 90 and substantially 90) with respect to the centerline C as viewed from above. The second position is a position where the water resistance body 93 is parallel to the front-rear direction. In this position, the water resistance body 93 defines an angle of 0 (hereinafter, 0 includes both 0 and substantially 0) with respect to the centerline C as viewed from above.

[0028] When at least a portion of the water resistance body 93 is submerged (e.g., when in the lowered position), the resistance received from the water in a predetermined direction (the front-rear direction in this example embodiment) is at a first magnitude in the first position (90) and at a second magnitude, smaller than the first magnitude, in the second position (0). In contrast, when the entire water resistance body 93 is above the water surface, the resistance it receives from the water is zero.

[0029] FIG. 3 is a block diagram of a marine propulsion system including the control device for a marine vessel according to an example embodiment.

[0030] The marine propulsion system includes the controller 70, the outboard motor 4, the trolling motor 5, the steering wheel 11, the remote control unit 12, the joystick 13, a display 14, various sensors 15, various manual operators 16, and a memory 17. The marine propulsion system further includes the water resistance switch 30, a first global navigation satellite system (GNSS) sensor 31, a second GNSS sensor 32, a wind speed sensor 33, a tidal current sensor 34, and the water resistance assemblies 90L and 90R.

[0031] The water resistance switch 30 includes a left switch 30L and a right switch 30R, which are used to manually operate the water resistance bodies 93 of the water resistance assemblies 90L and 90R, respectively.

[0032] The controller 70 may include a CPU 71, a ROM 72, a RAM 73, and a timer (not illustrated), or processor circuitry configured to perform similar functions. The ROM 72 stores a control program. The CPU 71 loads the control program stored in the ROM 72 into the RAM 73 and executes it, thus implementing various control operations. The RAM 73 provides a workspace for the CPU 71 to execute the control program.

[0033] The outboard motor 4 includes an engine control unit (ECU) 81, a steering control unit (SCU) 82, a rotational speed sensor 83, an engine 84, a steering mechanism 85, various sensors 86, a steering angle sensor 87, and various actuators 88. The ECU 81 and the SCU 82 each include a CPU (not illustrated). The ECU 81 is configured or programmed to control the driving of the engine 84 according to commands from the controller 70. The SCU 82 is configured or programmed to control the driving of the steering mechanism 85 according to commands from the controller 70.

[0034] The steering mechanism 85 causes the outboard motor body 20 to pivot about the steering axis center K (see FIG. 1A), thus changing the orientation of the outboard motor body 20 in the left-right direction. This changes the direction of the propulsive force acting on the stern, where the outboard motor body 20 is mounted. The steering mechanism 85 may be either electric or hydraulic. The various actuators 88 may include a power trim and tilt (PTT) mechanism that causes the outboard motor 4 to pivot about the tilt axis.

[0035] The rotational speed sensor 83 detects the rotation rate (revolutions per unit time) of the engine 84. The various sensors 86 include a throttle opening sensor and the like. The steering angle sensor 87 detects the actual steering angle of the outboard motor 4. Note that the controller 70 may also obtain the actual steering angle from the steering command value output to the steering mechanism 85.

[0036] The trolling motor 5 includes an electric motor 50, a propeller (not illustrated) that generates a propulsive force when driven to rotate by the electric motor 50, and an electric steering unit 56 that rotates the electric motor 50 about the rotation axis J2.

[0037] The steering unit 56 includes, for example, a servo motor. The orientation of the trolling motor 5 can be changed by the steering operation of the steering unit 56. Specifically, the steering unit 56 rotates the electric motor 50 about the rotation axis J2 to change its orientation within a range of 360 degrees or more, thus altering the direction of the propulsive force. This changes the steering angle of the trolling motor 5, which in turn changes the direction of the propulsive force that the trolling motor 5 exerts on the hull 2.

[0038] The trolling motor 5 includes, in addition to the electric motor 50 and the steering unit 56, a motor control unit (MCU) 57, an SCU 58, a steering angle sensor 55, various sensors 60, and an actuator 61.

[0039] The MCU 57 and the SCU 58 each include a CPU (not illustrated). The MCU 57 is configured or programmed to control the driving of the electric motor 50 according to commands from the controller 70. The maximum output of the electric motor 50 may be less than that of the engine 84 of the outboard motor 4. The SCU 58 is configured or programmed to control the driving of the steering unit 56 according to commands from the controller 70, thus changing the direction of the propulsive force acting on the bow, where the trolling motor 5 is mounted.

[0040] The actuator 61 moves the trolling motor 5 between a use position and a storage position. Note that it is not essential to provide a function to enable the trolling motor 5 to transition between the use position and the storage position by power.

[0041] The steering angle sensor 55 detects the steering angle of the trolling motor 5, which changes in response to the steering operation of the steering unit 56. Detection signals from the steering angle sensor 55 and the various sensors 60 are supplied to the controller 70. It is not essential that the hull 2, the outboard motor 4, and the trolling motor 5 be equipped with all the sensors and actuators mentioned above.

[0042] Strictly speaking, the points where the propulsive forces of the propulsion devices act are their respective mounting locations on the hull 2. However, for convenience of explanation, it is assumed herein that the propulsive force of the trolling motor 5 acts on the bow, and the propulsive force of the outboard motor 4 acts at the location of the attachment mechanism at the stern.

[0043] The various sensors 15 include a hull speed sensor, a hull acceleration sensor, an orientation sensor, a distance sensor, an attitude sensor, and a position sensor (not illustrated). The various sensors 15 further include a sensor that detects the operation of the remote control unit 12, a sensor that detects the rotational angle position of the steering wheel 11, a sensor that detects the operation of each switch and paddle on the steering wheel 11, and a sensor that detects the operation of the joystick 13. The hull speed sensor detects the navigation speed (vessel speed V1) of the marine vessel 1 (hull 2). Detection signals from the various sensors 15 are supplied to the controller 70.

[0044] The various operators 16 include not only operators to maneuver the marine vessel but also setting operators to make various settings and input operators to enter various instructions (not illustrated). Some of the various operators 16 may be located on the steering wheel 11. The various operators 16 are operated by the vessel operator, and the operation signals are supplied to the controller 70. The memory 17 is a read-write non-volatile storage medium.

[0045] The controller 70 may establish predetermined communication with the various sensors 15 and the various operators 16 to exchange information with them. The display 14 displays various types of information.

[0046] The first GNSS sensor 31 and the second GNSS sensor 32 periodically receive GNSS signals from GNSS satellites. As a result, the controller 70 can acquire the current position of each of the GNSS sensors 31 and 32. The first GNSS sensor 31 and the second GNSS sensor 32 are located at different positions. For example, the first GNSS sensor 31 and the second GNSS sensor 32 are arranged at different positions along the front-rear direction. Accordingly, it is possible to determine the hull orientation based on the signals received by the GNSS sensors 31 and 32, without the need for an orientation sensor.

[0047] The wind speed sensor 33 detects the wind speed WS. The tidal current sensor 34 detects the relative tidal current speed and relative tidal current direction as observed from the hull 2. The configuration of the tidal current sensor 34 is not particularly limited. For example, the tidal current sensor 34 may emit ultrasonic waves at an angle into the sea and analyze the reflected ultrasonic waves to determine the relative tidal current speed and relative tidal current direction.

[0048] The controller 70 determines the absolute tidal current speed TV1 based on the relative tidal current speed and the vessel speed V1. The controller 70 also determines the absolute tidal current direction based on the relative tidal current direction and the direction of the vessel's movement. Hereinafter, unless otherwise specified, the terms tidal current speed and tidal current direction will refer to the absolute tidal current speed TV1 and the absolute tidal current direction, respectively.

[0049] In an example embodiment, there are a plurality of vessel maneuvering modes, which can be broadly classified into an outboard motor mode that does not utilize the trolling motor 5 and a cooperative mode that utilizes both the trolling motor 5 and the outboard motor 4. The outboard motor mode is a maneuvering mode in which the outboard motor 4 is controlled primarily based on the rotational operation of the steering wheel 11 and the operation of the remote control unit 12. Other maneuvering modes include a drift fishing mode, which utilizes the water resistance assemblies 90L and 90R to achieve operations suitable for drift fishing. In the drift fishing mode, the trolling motor 5 and/or the outboard motor 4 may also be used.

[0050] FIG. 4 is a flowchart of a drift fishing mode process. This process is implemented by the CPU 71, which loads a program stored in the ROM 72 or the like into the RAM 73 and executes it. The process is initiated according to an instruction to start the drift fishing mode received through the various operators 16.

[0051] After the process starts, the CPU 71 monitors the outputs of the sensors and the like and acquires the latest values of the hull orientation, tidal current direction, wind speed WS, vessel speed V1, and absolute tidal current speed TV1 at regular time intervals. Specifically, the CPU 71, configured or programmed to function as a first acquisition unit, acquires the wind speed WS; the CPU 71, configured or programmed to function also as a second acquisition unit, acquires the absolute tidal current speed TV1, comparison value TV2, and tidal current direction; and the CPU 71, configured or programmed to function also as a third acquisition unit, acquires the hull orientation and vessel speed V1. In this process, the CPU 71 is configured or programmed to control the water resistance bodies 93 and the like based on at least the wind speed WS and the absolute tidal current speed TV1.

[0052] In step S101, the CPU 71 determines whether the hull orientation is parallel to the tidal current direction. The CPU 71 determines that the hull orientation is parallel to the tidal current direction if, for example, the angular deviation between them does not exceed a predetermined angle. If the hull orientation is parallel to the tidal current direction, the process proceeds to step S102. If the hull orientation is not parallel to the tidal current direction, the process proceeds to step S104.

[0053] In step S102, the CPU 71 first calculates a comparison value TV2, which is a value derived from the absolute tidal current speed TV1, by multiplying the absolute tidal current speed TV1 by a correction coefficient. For example, the correction coefficient is . Here, the comparison value TV2 is a value obtained by correcting the absolute tidal current speed TV1 to allow an appropriate comparison with the wind speed WS.

[0054] The correction coefficient is not limited to , nor is the correction method restricted. The CPU 71 then determines whether a predetermined condition is satisfied that at least one of the following applies: the wind speed WS exceeds a predetermined speed WS0 (WS0<WS), or the wind speed WS is greater than the comparison value TV2 (TV2<WS).

[0055] If the CPU 71 determines that the predetermined condition is satisfied, the process proceeds to step S103. If the predetermined condition is not satisfied, the process proceeds to step S105.

[0056] FIGS. 5A and 5B are schematic diagrams illustrating an example of the control of the water resistance bodies 93. In step S103, the CPU 71 sets both the water resistance bodies (the water resistance bodies 93 of the water resistance assemblies 90L and 90R) to the first position (90), as illustrated in FIG. 5A. In the case where step S103 is performed, the wind speed WS has a significant effect on the hull 2, and the hull 2 is highly likely to move substantially differently from the tidal current. Therefore, by setting both the water resistance bodies 93 to the first position, the extent to which the movement of the hull 2 depends on the tidal current can be increased. In effect, this acts as a brake on the hull 2 to resist the force exerted by the wind speed WS. As a result, the hull 2 and fishing lines are restrained from moving differently, making the fishing environment easier.

[0057] In step S105, the CPU 71 sets both the water resistance bodies (the water resistance bodies 93 of the water resistance assemblies 90L and 90R) to the second position (0), as illustrated in FIG. 5B. In the case where step S105 is performed, the wind speed WS has little effect on the hull 2, and the hull 2 is less likely to move substantially differently from the tidal current. Therefore, by setting both the water resistance bodies 93 to the second position, the hull 2 primarily moves along with the tidal current.

[0058] Although FIGS. 5A and 5B illustrate an example in which both the tide and the wind are directed from front to rear, steps S103 and S105 can also be applied to cases where they are directed from rear to front, or where they are directed in opposite directions.

[0059] FIGS. 6A to 6C are schematic diagrams illustrating an example of the transition in the movement of the hull 2 when the wind direction and the tidal current direction are not parallel.

[0060] As illustrated in FIG. 6A, when the hull 2 is subjected to a crosswind while receiving the tidal current from the front, primarily the bow is urged by a force in the direction F1, causing the hull 2 to turn. Eventually, the hull orientation and the tidal current direction are no longer parallel (FIG. 6B). Accordingly, in step S104, the CPU 71 performs an angular deviation correction control. For example, as illustrated in FIG. 6C, the CPU 71 sets one of the water resistance bodies (one of the water resistance bodies 93 of the water resistance assemblies 90L and 90R) to the first position and another one (the other of the water resistance bodies 93 of the water resistance assemblies 90L and 90R) to the second position. Step S104 is performed regardless of whether the above predetermined condition is satisfied (without the need to determine whether the predetermined condition is satisfied).

[0061] In the example of FIG. 6C, the hull 2 is subjected to wind from the right; therefore, it is appropriate to generate an urging force on the bow in the direction F2, which is opposite to the direction F1. Accordingly, in this case, the CPU 71 sets the water resistance body 93 of the water resistance assembly 90R to the first position and sets the water resistance body 93 of the water resistance assembly 90L to the second position.

[0062] That is, the water resistance body 93 is set to the first position (90) is the one that generates a rotational moment on the hull 2 in a direction to correct the angular deviation. In the example of FIG. 6C, this corresponds to the water resistance body 93 of the water resistance assembly 90R. When the water resistance body 93 of the water resistance assembly 90R is in the first position, it is subjected to resistance from the tidal current causing a clockwise turning force about the center of gravity G to be exerted on the hull 2. As a result, the angular deviation is reduced. Such control makes it easier to maintain the hull orientation parallel to the tidal current direction, thus maintaining a favorable fishing environment.

[0063] Incidentally, in the example illustrated in FIGS. 6A to 6C, it is assumed that once the angular deviation is corrected, the water resistance body 93 of the water resistance assembly 90R returns to the first position. Therefore, it is assumed that the control continues to switch the water resistance body 93 of the water resistance assembly 90R between the first and second positions.

[0064] After steps S103, S104, and S105, the process proceeds to step S106. In step S106, the CPU 71 performs the following process to determine whether a speed correction control is required. First, the CPU 71 determines the hull speed V2, which is the speed of the hull 2 in the tidal current direction, based on the vessel speed V1 and the hull orientation. Next, the CPU 71 determines whether the difference (absolute value) between the hull speed V2 in the tidal current direction and the absolute tidal current speed TV1 exceeds a predetermined difference V0. If the CPU 71 determines that the difference does not exceed the predetermined difference V0, the process proceeds to step S108. If the difference exceeds the predetermined difference V0, the process proceeds to step S107.

[0065] In step S107, the CPU 71 performs the speed correction control. This is because it is considered that the movement of the hull 2 does not follow the tidal current due to wind effects. In the speed correction control, the CPU 71 corrects the hull speed V2 using the outboard motor 4 and the trolling motor 5. Specifically, aiming to match the hull speed V2 with the absolute tidal current speed TV1, the CPU 71 is configured or programmed to control the outboard motor 4 and the trolling motor 5 such that the above difference is at most the predetermined difference V0. The speed correction control may also involve controlling the water resistance bodies 93 of the water resistance assemblies 90L and 90R. This restores the positional relationship between the hull 2 and fishing lines to an appropriate state.

[0066] After step S107, the process proceeds to step S108. In step S108, the CPU 71 performs other processes, and the process then returns to step S101. The other processes include those performed according to user instructions, such as processes based on other operations, a mode-switching process, and a process for terminating this process.

[0067] According to the present example embodiment, the water resistance bodies 93 are controlled based on the wind speed and the tidal current speed so that the movement of the hull 2 mainly follows the tidal current and becomes closer to the movement pattern of the fishing line, even under strong wind conditions. Thus, it is possible to provide a comfortable drift fishing environment.

[0068] In addition, when the difference between the hull speed V2 in the tidal current direction and the absolute tidal current speed TV1 exceeds the predetermined difference V0, the speed correction control is performed using the outboard motor 4 and the trolling motor 5. Therefore, in cases where controlling the water resistance bodies 93 is insufficient, the movements of the hull 2 and the fishing line can be brought closer together, providing an easy drift fishing environment.

[0069] Note that the water resistance assemblies 90L and 90R need not necessarily be located at the stern. As long as they are provided in a pair on the left and right sides as illustrated in FIGS. 7A and 7B, their locations are not particularly limited.

[0070] FIGS. 7A and 7B are schematic diagrams illustrating modifications to the configuration of the water resistance assemblies 90L and 90R. As illustrated in FIG. 7A, the water resistance assemblies 90L and 90R may be located on the left and right sides of the hull 2, respectively. Alternatively, as illustrated in FIG. 7B, the water resistance assemblies 90L and 90R may be configured in a pair, one on the left side and one on the right side, near the bow.

[0071] The water resistance bodies 93 are preferably provided as a pair, one on the left and one on the right of the hull, but there may be three or more of the water resistance bodies 93.

[0072] In configuring the water resistance bodies 93 such that the magnitude of resistance they receive from the water in a predetermined direction differs when they are in the first position and when they are in the second position, it is not essential that the predetermined direction be the front-rear direction, and the direction may be arbitrary. The water resistance bodies 93 need not necessarily be plate-shaped (e.g., relatively thin and flat structures), and may have other shapes. It is also not essential that the water resistance bodies 93 at the first position and at the second position be perpendicular to each other.

[0073] Although the present example embodiment includes two motors, the outboard motor 4 and the trolling motor 5, as propulsion devices, it suffices if two or more propulsion devices are provided to enable the hull 2 to turn. For example, one propulsion device may be provided at the bow, and two propulsion devices may be provided on either side of the stern. It is not essential that the propulsion devices each have an engine, and one or more may be electrically powered.

[0074] In addition, although the water resistance bodies 93 have been described as having their positions adjustable in two steps, they are not limited to this and may be configured for continuous adjustment or adjustment in three or more steps. For example, a trim tab may be used. Furthermore, the water resistance bodies 93 need not necessarily be configured to pivot underwater and may be of a type that moves between an above-water position and an underwater position, such as a protruding type. If the water resistance bodies 93 are configured for continuous adjustment or adjustment in three or more steps, the left and right water resistance bodies 93 can be controlled to protrude by different amounts in the angular deviation correction control (S104).

[0075] If the focus is solely on reducing or preventing differing movements between the hull 2 and fishing lines through a simple control to improve the drift fishing environment, it is not essential to include the angular deviation correction control (S104) or the speed correction control (S107).

[0076] 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.