A boat propulsor includes a duct, a propeller in the duct and rotatable around a rotation axis extending along an axial direction of the duct, and a rotator to rotate the propeller. An upper portion of the duct includes a plate extending from the duct in the axial direction and including holes. Water streams passing around and along the duct are attenuated as the water streams pass through the holes in the plate.

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.

The invention relates to a device for reducing the driving power requirement of a watercraft, comprising a flow guiding surface from which at least one first fin projects. A first end of said first fin is fixed to the flow guiding surface, and a second end of the first fin is embodied as a free end.

The invention relates to a device for reducing the driving power requirement of a watercraft, comprising a flow guiding surface from which at least one first fin projects. A first end of said first fin is fixed to the flow guiding surface, and a second end of the first fin is embodied as a free end.

The present invention is a combination apparatus having a body with two separate mating arms made of sacrificial anode material and a pair of oppositely disposed removable cutting blades made of material such as stainless steel. A respective cutting blade extends through an interior of a respective mating arm and extends outwardly from an exterior surface of a respective mating arm with cutting teeth of each respective cutting blade aligned with a slope of the exterior surface of a respective mating arm.

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 aquatic vessel may include contra-rotating propellers and a hull mold with a keel pad sectional extended from a hull planing surface to a location on the hull mold at which a propeller shaft exits a propeller shaft tunnel at an aft transom edge of the hull mold and at a forward portion of the keel pad sectional, with sides of the propeller shaft tunnel formed into directional ports to increase a flow of water into the propeller shaft tunnel.

An aquatic vessel may include contra-rotating propellers and a hull mold with a keel pad sectional extended from a hull planing surface to a location on the hull mold at which a propeller shaft exits a propeller shaft tunnel at an aft transom edge of the hull mold and at a forward portion of the keel pad sectional, with sides of the propeller shaft tunnel formed into directional ports to increase a flow of water into the propeller shaft tunnel.

A hull mold of an aquatic vessel may include a keel pad sectional extended from a hull planing surface to a location on the hull mold at which a propeller shaft exits a propeller shaft tunnel at an aft transom edge of the hull mold and/or at a forward portion of the keel pad sectional, with sides of the propeller shaft tunnel formed into directional ports to increase a flow of water into the propeller shaft tunnel.

A hull mold of an aquatic vessel may include a keel pad sectional extended from a hull planing surface to a location on the hull mold at which a propeller shaft exits a propeller shaft tunnel at an aft transom edge of the hull mold and/or at a forward portion of the keel pad sectional, with sides of the propeller shaft tunnel formed into directional ports to increase a flow of water into the propeller shaft tunnel.