Patent ID: 7115007

Claim:
A stern unit for mounting to a stern end of a marine craft, the stern unit comprising: a shaft which transmits torque produced by an inboard engine linearly; a propeller activated by and located at a front end of said shaft; at least one rudder located in front of the propeller guiding the marine craft; a steering assembly comprising a hydraulic cylinder and a piston, wherein the at least one rudder is maneuvered by the steering assembly; and a casing having a bottom surface with a parabolic cross sectional profile and providing a housing to the shaft, the propeller, and the at least one rudder, the casing being spaced with the stern end so as to provide a gap between the casing and the stern end above a trace line of a marine craft bottom, a portion of the bottom surface sloping downwardly away from the stern end and extending below the trace line, wherein air is sucked at the gap above water surface line creating an air film which extends inside the casing along the bottom surface to an outlet of the casing to reduce the frictional resistance between the flowing water and the casing surface; and wherein the hydraulic cylinder and the piston of the steering assembly are mounted on the casing.