A boat maneuvering control method for a boat includes setting a target boat speed, detecting an actual boat speed of the boat, and acquiring a base engine rotational speed associated with the target boat speed that is set, correcting the base engine rotational speed according to a difference between the target boat speed and the actual boat speed so as to set the base engine rotational speed that is corrected as a target engine rotational speed, and controlling an engine based on the target engine rotational speed that is set such that the actual boat speed approaches the target boat speed.

A boat maneuvering control method for a boat includes setting a target boat speed, detecting an actual boat speed of the boat, and acquiring a base engine rotational speed associated with the target boat speed that is set, correcting the base engine rotational speed according to a difference between the target boat speed and the actual boat speed so as to set the base engine rotational speed that is corrected as a target engine rotational speed, and controlling an engine based on the target engine rotational speed that is set such that the actual boat speed approaches the target boat speed.

An outdrive for a marine vessel, such as a watercraft having an inboard engine, is provided. The outdrive can include an upper drive unit having a driveshaft that rotates in response to rotation of an input shaft coupled to an engine within a hull of the watercraft. The upper drive unit is movably joined with a lower drive unit, which includes a propeller shaft that rotates in response to rotation of the driveshaft, and an associated propeller. The lower drive unit is movable from a raised mode, in which it is adjacent the upper drive unit, to a lowered mode, in which it is a preselected distance from the upper drive unit, thereby lowering a thrust point produced by the propeller, all while the watercraft is moving through water and while the propeller is producing thrust. A related method and outdrive upper unit are also provided.

An outdrive for a marine vessel, such as a watercraft having an inboard engine, is provided. The outdrive can include an upper drive unit having a driveshaft that rotates in response to rotation of an input shaft coupled to an engine within a hull of the watercraft. The upper drive unit is movably joined with a lower drive unit, which includes a propeller shaft that rotates in response to rotation of the driveshaft, and an associated propeller. The lower drive unit is movable from a raised mode, in which it is adjacent the upper drive unit, to a lowered mode, in which it is a preselected distance from the upper drive unit, thereby lowering a thrust point produced by the propeller, all while the watercraft is moving through water and while the propeller is producing thrust. A related method and outdrive upper unit are also provided.

An outdrive for a marine vessel, such as a watercraft having an inboard engine, is provided. The outdrive can include an upper drive unit having a driveshaft that rotates in response to rotation of an input shaft coupled to an engine within a hull of the watercraft. The upper drive unit is movably joined with a lower drive unit, which includes a propeller shaft that rotates in response to rotation of the driveshaft, and an associated propeller. The lower drive unit is movable from a raised mode, in which it is adjacent the upper drive unit, to a lowered mode, in which it is a preselected distance from the upper drive unit, thereby lowering a thrust point produced by the propeller, all while the watercraft is moving through water and while the propeller is producing thrust. A related method and outdrive upper unit are also provided.

Disclosed are a propulsion device for a ship and a ship having same. The propulsion device, according to an embodiment of the present invention, comprises: a rear propeller fixed to a driveshaft; a front propeller positioned in front of the rear propeller, and supported rotably on the driveshaft; and a counter rotation device for reversing and transmitting the rotation of the driveshaft to the front propeller; a motor for rotating the driveshaft; and an housing, which extends from to the lower part of the hull, and which is installed so as to envelope the counter rotation device and the motor.

Disclosed are a propulsion device for a ship and a ship having same. The propulsion device, according to an embodiment of the present invention, comprises: a rear propeller fixed to a driveshaft; a front propeller positioned in front of the rear propeller, and supported rotably on the driveshaft; and a counter rotation device for reversing and transmitting the rotation of the driveshaft to the front propeller; a motor for rotating the driveshaft; and an housing, which extends from to the lower part of the hull, and which is installed so as to envelope the counter rotation device and the motor.

Objects of the present invention are provide an evaluation method of ship propulsive performance in actual seas, an evaluation program of ship propulsive performance in actual seas and an evaluation system of ship propulsive performance in actual seas capable of precisely evaluating ship propulsive performance in actual seas on the same scale also before the ship sails for example. As solving means of the objects, a standard sailing model 2 of the ship in actual seas is set, a sailing condition of the ship and a ship condition of the ship are input to the standard sailing model 2, the standard sailing model 2 into which the sailing condition and the ship condition are input and the ship condition are applied to a previously verified calculating method 1 of ship performance in actual seas, and ship propulsive performance in actual seas is evaluated.

Objects of the present invention are provide an evaluation method of ship propulsive performance in actual seas, an evaluation program of ship propulsive performance in actual seas and an evaluation system of ship propulsive performance in actual seas capable of precisely evaluating ship propulsive performance in actual seas on the same scale also before the ship sails for example. As solving means of the objects, a standard sailing model 2 of the ship in actual seas is set, a sailing condition of the ship and a ship condition of the ship are input to the standard sailing model 2, the standard sailing model 2 into which the sailing condition and the ship condition are input and the ship condition are applied to a previously verified calculating method 1 of ship performance in actual seas, and ship propulsive performance in actual seas is evaluated.

A boat maneuvering control method for a boat includes setting a target boat speed, detecting an actual boat speed of the boat, and acquiring a base engine rotational speed associated with the target boat speed that is set, correcting the base engine rotational speed according to a difference between the target boat speed and the actual boat speed so as to set the base engine rotational speed that is corrected as a target engine rotational speed, and controlling an engine based on the target engine rotational speed that is set such that the actual boat speed approaches the target boat speed.