System for aiding the planing of a planing boat comprising a hull, having a critical transition speed from a displacement sailing and a planing sailing and at least an internal combustion engine comprising means for transmitting an engine displaced power to the water; transmission means defining a gear ratio and identifying a critical speed of rotation of the engine corresponding to the critical speed of the hull; the system comprises a centrifugal supercharger, for supercharging said internal combustion engine, activated by speed multiplying means to be operating in a predetermined interval of speeds of the at least an internal combustion engine including said critical engine speed.

A jet propelled watercraft includes a vessel body, a jet propulsion mechanism, a bucket, and a controller. The jet propulsion mechanism is configured to propel the vessel body. The controller is configured and programmed to control a thrust of the jet propulsion mechanism to propel the vessel body. The bucket is configured to move to a retracted position spaced away from the jet of water ejected from the jet propulsion mechanism and a jet receiving position to receive the jet of water ejected from the jet propulsion mechanism. The controller is configured and programmed to change an increase rate of the thrust in accordance with a forward speed of the vessel body until the thrust is increased to a predetermined value after the bucket has been moved from the retracted position to the jet receiving position.

The invention provides an internal combustion engine comprising a piston mounted for reciprocating linear motion within a cylinder along a cylinder axis. The piston is coupled to an output shaft by a power transfer assembly arranged to convert linear motion of the piston to rotary motion of the output shaft. The piston has a first head moveable within a first chamber and a second head opposite the first head and moveable within a second chamber. The power transfer assembly has a lubrication system for lubricating moving components of the power transfer assembly. The lubrication system is sealed from the first chamber and the second chamber to prevent the passage of fluid from the lubrication system into the first chamber and the second chamber.

The invention provides an internal combustion engine comprising a piston mounted for reciprocating linear motion within a cylinder along a cylinder axis. The piston is coupled to an output shaft by a power transfer assembly arranged to convert linear motion of the piston to rotary motion of the output shaft. The piston has a first head moveable within a first chamber and a second head opposite the first head and moveable within a second chamber. The power transfer assembly has a lubrication system for lubricating moving components of the power transfer assembly. The lubrication system is sealed from the first chamber and the second chamber to prevent the passage of fluid from the lubrication system into the first chamber and the second chamber.

A fluid intake/discharge valve body for suction of a cryogenic liquefied gas fluid into a cylinder liner and discharge of the gas fluid with a piston, includes: a valve seat body including a fluid supply portion to supply the fluid and a fluid exhaust portion; an intake valve biased against the fluid supply portion; and a discharge valve biased against the fluid exhaust portion. The fluid supply portion includes a supply pathway connected to a supply pipe; a dividing wall including intake holes facing the intake valve; and a counterbore recessed portion on the dividing wall to surround the intake holes. The intake valve abuts an edge of the recessed portion when biased against the fluid supply portion. The discharge valve receives fluid pressure from a side of the discharge hole including a recessed portion disposed in a region wider than an outer periphery of the discharge hole.

A fluid intake/discharge valve body for suction of a cryogenic liquefied gas fluid into a cylinder liner and discharge of the gas fluid with a piston, includes: a valve seat body including a fluid supply portion to supply the fluid and a fluid exhaust portion; an intake valve biased against the fluid supply portion; and a discharge valve biased against the fluid exhaust portion. The fluid supply portion includes a supply pathway connected to a supply pipe; a dividing wall including intake holes facing the intake valve; and a counterbore recessed portion on the dividing wall to surround the intake holes. The intake valve abuts an edge of the recessed portion when biased against the fluid supply portion. The discharge valve receives fluid pressure from a side of the discharge hole including a recessed portion disposed in a region wider than an outer periphery of the discharge hole.

A jet propelled watercraft includes a reverse gate that moves to a first position and to a second position. When the reverse gate is in the first position, the reverse gate causes a vessel body to move forward. When the reverse gate is in the second position, the reverse gate causes the vessel body to decelerate or move backward. A velocity mode selector is used to select a normal mode or a velocity mode. The velocity mode has a maximum velocity different from that of the normal mode. When the reverse gate is in the second position and the velocity mode is selected, a controller is configured or programmed to set an upper limit of an engine rotation speed in the velocity mode to be different from that of the engine rotation speed in the normal mode.

A jet propelled watercraft includes a reverse gate that moves to a first position and to a second position. When the reverse gate is in the first position, the reverse gate causes a vessel body to move forward. When the reverse gate is in the second position, the reverse gate causes the vessel body to decelerate or move backward. A velocity mode selector is used to select a normal mode or a velocity mode. The velocity mode has a maximum velocity different from that of the normal mode. When the reverse gate is in the second position and the velocity mode is selected, a controller is configured or programmed to set an upper limit of an engine rotation speed in the velocity mode to be different from that of the engine rotation speed in the normal mode.

An outboard motor includes an engine, a propeller shaft that rotates together with a propeller and extends in a forward-rearward direction, and a lower case that houses the propeller shaft. The lower case includes a front case and a rear case separate from the front case and positioned rearward of the front case, and the front case and the rear case are assembled to each other.

An outboard motor includes an engine, a propeller shaft that rotates together with a propeller and extends in a forward-rearward direction, and a lower case that houses the propeller shaft. The lower case includes a front case and a rear case separate from the front case and positioned rearward of the front case, and the front case and the rear case are assembled to each other.