An accelerating ducted propeller system for propelling boats offers enhanced performance, having the front end of the nozzle disposed at a radial distance (H) between 0.045D and 0.082D from the inner radius of the nozzle, where D is the inner diameter of the nozzle. The front end of the chord of the axial profile of the nozzle has a larger radius than the rear end of the chord with respect to the axis of rotation of the propeller. The inner surface of the nozzle at the axial distance (J) of 0.025D from the rear end of the output edge of the nozzle is at a radial distance from the inner radius of the nozzle of more than 0.0040D and less than 0.0300D. The radial difference between the inner radius of the nozzle and the outer radius of the profile of the nozzle is less than 0.092D.

A boat propeller includes a gear box, an impeller, a stream-guiding ring, and a stream-shaping nozzle. The gear box has a casing and a transmission shaft partially received in the casing. The impeller has an impeller shaft and vanes. The impeller shaft has a hollow columnar outer shaft housing and a hollow columnar inner shaft housing. The inner and outer shaft housings are connected using a plurality of rib portions. The inner shaft housing is further connected to the transmission shaft of the gear box. The vanes are integrated formed on an outer peripheral surface of the outer shaft. The stream-guiding ring is assembled to the casing of the gear box to house the impeller. The stream-shaping nozzle is connected to a rear end of the stream-guiding ring for providing stream-shaping effects. Thereby, the boat propeller has its water inlet diameter maximized, which helps to improve propulsive efficiency.

A ship handling device enabling easy turning calibration. With a ship handling device (7), during turning calibration with the ship handling device (7), the joystick lever (10) is turned to rotate the forward-backward propellers (4) on the port and starboard sides of the ship, and the joystick lever (10) is tilted to change a forward-thrust/backward-thrust ratio of the forward-backward propeller (4) on the port or starboard side or to change the rotation speeds. When a calibration execution switch (10a) is operated, thrusts generated with the changed forward-thrust backward-thrust ratio are set as correction coefficients, or, among thrusts generated at the changed rotation speeds (Npn, Nsn) of the forward-backward propellers (4) on the port and starboard sides, thrusts generated by the forward-backward propellers (4) on the port and starboard sides according to the tilting of the joystick lever (10) are set as correction coefficients (Cp, Cs).

A ship handling device enabling easy turning calibration. With a ship handling device (7), during turning calibration with the ship handling device (7), the joystick lever (10) is turned to rotate the forward-backward propellers (4) on the port and starboard sides of the ship, and the joystick lever (10) is tilted to change a forward-thrust/backward-thrust ratio of the forward-backward propeller (4) on the port or starboard side or to change the rotation speeds. When a calibration execution switch (10a) is operated, thrusts generated with the changed forward-thrust backward-thrust ratio are set as correction coefficients, or, among thrusts generated at the changed rotation speeds (Npn, Nsn) of the forward-backward propellers (4) on the port and starboard sides, thrusts generated by the forward-backward propellers (4) on the port and starboard sides according to the tilting of the joystick lever (10) are set as correction coefficients (Cp, Cs).

A portable propulsion system for a watercraft may include a shaft, a propeller, an outer casing, and a flexible strap. The shaft may have a prop end section, a drive end section, and a rotational axis extending from the prop end section to the drive end section. The propeller may be connected to the prop end section of the shaft. The drive end section may be configured for removable connection to a driver for rotation of the propeller via rotation of the shaft about the rotational axis to propel the watercraft. The outer casing may be disposed around the shaft. The flexible strap may have first and second end sections connected to the outer casing in respective first and second regions.

An improved boat and drive assembly intended for a boat used in a primary shallow water environment has a hull with an integrated closed internal engine heat exchanger and a drive assembly that includes a ring-within-a-ring steering mechanism and an obstacle resistant shoe plate. Stabilizer fins positioned above the shoe plate at a position forward of the spinning propeller allow air and water to exit from the rear of the stabilizer fins away from the spinning propeller. The heat exchanger assembly may include an axillary cooling tank and open heat dissipation system having a raw water reservoir continuously filled with raw water drawn directly from the waterway on which the boat is propelled to enhance the cooling capacity of the integrated internal engine heat exchanger.

A device (100) has surfaces (21, 22, 23, 24) and an anti-biofouling system (10) comprising at least one light source (11, 12) for performing an anti-biofouling action on at least a majority of the surfaces (21, 22, 23, 24), the at least one light source (11, 12) being adapted to emit rays of anti-biofouling light. The surfaces (21, 22, 23, 24) are configured relative to each other and to the at least one light source (11, 12) such that during operation of the at least one light source (11, 12), at least a majority of the surfaces (21, 22, 23, 24) is free from shadow with respect to the rays of anti-biofouling light from the at least one light source (11, 12), wherein it may be possible for the rays of anti-biofouling light to reach the surfaces (21, 22, 23, 24) by skimming along the surfaces (21, 22, 23, 24).

A device (100) has surfaces (21, 22, 23, 24) and an anti-biofouling system (10) comprising at least one light source (11, 12) for performing an anti-biofouling action on at least a majority of the surfaces (21, 22, 23, 24), the at least one light source (11, 12) being adapted to emit rays of anti-biofouling light. The surfaces (21, 22, 23, 24) are configured relative to each other and to the at least one light source (11, 12) such that during operation of the at least one light source (11, 12), at least a majority of the surfaces (21, 22, 23, 24) is free from shadow with respect to the rays of anti-biofouling light from the at least one light source (11, 12), wherein it may be possible for the rays of anti-biofouling light to reach the surfaces (21, 22, 23, 24) by skimming along the surfaces (21, 22, 23, 24).

A cover device for at least partially closing an underwater opening in a hull of a watercraft includes a variable-volume hollow-chamber lip assembly including at least two hollow-chamber lips and one buoyancy body. The at least one hollow-chamber lip is volume-variable by supplying a fluid to or removing a fluid from an interior thereof, and the at least one hollow-chamber lip assembly is shiftable between an expanded state and a contracted state by supplying or removing the fluid.

A cover device for at least partially closing an underwater opening in a hull of a watercraft includes a variable-volume hollow-chamber lip assembly including at least two hollow-chamber lips and one buoyancy body. The at least one hollow-chamber lip is volume-variable by supplying a fluid to or removing a fluid from an interior thereof, and the at least one hollow-chamber lip assembly is shiftable between an expanded state and a contracted state by supplying or removing the fluid.