A boat includes a planing hull, a propeller, a main rudder, and a pair of flanking rudders. The planing hull has port and starboard sides, a transom, a hull bottom, and a centerline running down the middle of the boat, halfway between the port and starboard sides. The propeller is positioned forward of the transom and beneath the hull bottom. The main rudder is positioned aft of the propeller. The main rudder has a rotation axis about which the main rudder rotates. The flanking rudders are positioned forward of the propeller. One of the flanking rudders is positioned on the port side of the centerline, and the other flanking rudder is positioned on the starboard side of the centerline.

A boat includes a planing hull, a propeller, a main rudder, and a pair of flanking rudders. The planing hull has port and starboard sides, a transom, a hull bottom, and a centerline running down the middle of the boat, halfway between the port and starboard sides. The propeller is positioned forward of the transom and beneath the hull bottom. The main rudder is positioned aft of the propeller. The main rudder has a rotation axis about which the main rudder rotates. The flanking rudders are positioned forward of the propeller. One of the flanking rudders is positioned on the port side of the centerline, and the other flanking rudder is positioned on the starboard side of the centerline.

A steering gear for a boat includes a steering mechanism that moves a rudder, and a driving source. The steering mechanism has: a housing that is fixed to a hull; an output shaft that is rotatably supported by the housing; a first conversion mechanism that is provided inside the housing and converts power from the driving source into rotation of the output shaft; and a second conversion mechanism that is provided outside the housing and converts rotation of the output shaft into motion of the rudder.

A steering gear for a boat includes a steering mechanism that moves a rudder, and a driving source. The steering mechanism has: a housing that is fixed to a hull; an output shaft that is rotatably supported by the housing; a first conversion mechanism that is provided inside the housing and converts power from the driving source into rotation of the output shaft; and a second conversion mechanism that is provided outside the housing and converts rotation of the output shaft into motion of the rudder.

A steering device includes: a cylinder; a normal/reverse rotation type hydraulic power source; an oil storage tank; a first oil passage that connects the cylinder with the hydraulic power source; a second oil passage that connects the cylinder with the hydraulic power source; an oil passage group that includes at least one oil passage connecting at least one of the first oil passage and the second oil passage with the oil storage tank; and a changeover valve group that performs changeover between a state in which hydraulic oil recovered from the cylinder flows back to the oil storage tank and a state in which hydraulic oil supplied from the hydraulic power source to the cylinder does not flow back to the oil storage tank, in accordance with a state of hydraulic oil supplied by the hydraulic power source.

A steering device includes: a cylinder; a normal/reverse rotation type hydraulic power source; an oil storage tank; a first oil passage that connects the cylinder with the hydraulic power source; a second oil passage that connects the cylinder with the hydraulic power source; an oil passage group that includes at least one oil passage connecting at least one of the first oil passage and the second oil passage with the oil storage tank; and a changeover valve group that performs changeover between a state in which hydraulic oil recovered from the cylinder flows back to the oil storage tank and a state in which hydraulic oil supplied from the hydraulic power source to the cylinder does not flow back to the oil storage tank, in accordance with a state of hydraulic oil supplied by the hydraulic power source.

A hydraulic steering system for vehicles includes a steering control member; a hydraulic pump provided with a rotatable driving shaft on which the control member is fitted; a hydraulic actuating cylinder connected with two ports of the pump alternately operating as delivery side and return side of the pump and mechanically connected with a direction changing member, which determines a change in the direction by modifying orientation via an actuating cylinder as a function of the supply of hydraulic fluid to the cylinder from the pump by the steering control member. The driving shaft is dynamically connected with an electric motor/transmission assembly, which is activated alternatively by generating a rotational force auxiliary to the movement manually exerted on the steering control member or opposing the manually exerted movement, or by driving to rotate the driving shaft of the pump in place of the manual action driving the steering control member.

A hydraulic steering system for vehicles includes a steering control member; a hydraulic pump provided with a rotatable driving shaft on which the control member is fitted; a hydraulic actuating cylinder connected with two ports of the pump alternately operating as delivery side and return side of the pump and mechanically connected with a direction changing member, which determines a change in the direction by modifying orientation via an actuating cylinder as a function of the supply of hydraulic fluid to the cylinder from the pump by the steering control member. The driving shaft is dynamically connected with an electric motor/transmission assembly, which is activated alternatively by generating a rotational force auxiliary to the movement manually exerted on the steering control member or opposing the manually exerted movement, or by driving to rotate the driving shaft of the pump in place of the manual action driving the steering control member.

A steering device includes: a cylinder; a normal/reverse rotation type hydraulic power source; an oil storage tank; a first oil passage that connects the cylinder with the hydraulic power source; a second oil passage that connects the cylinder with the hydraulic power source; an oil passage group that includes at least one oil passage connecting at least one of the first oil passage and the second oil passage with the oil storage tank; and a changeover valve group that performs changeover between a state in which hydraulic oil recovered from the cylinder flows back to the oil storage tank and a state in which hydraulic oil supplied from the hydraulic power source to the cylinder does not flow back to the oil storage tank, in accordance with a state of hydraulic oil supplied by the hydraulic power source.

A steering device includes: a cylinder; a normal/reverse rotation type hydraulic power source; an oil storage tank; a first oil passage that connects the cylinder with the hydraulic power source; a second oil passage that connects the cylinder with the hydraulic power source; an oil passage group that includes at least one oil passage connecting at least one of the first oil passage and the second oil passage with the oil storage tank; and a changeover valve group that performs changeover between a state in which hydraulic oil recovered from the cylinder flows back to the oil storage tank and a state in which hydraulic oil supplied from the hydraulic power source to the cylinder does not flow back to the oil storage tank, in accordance with a state of hydraulic oil supplied by the hydraulic power source.