Abstract: A propulsion system of displacement or semi-displacement ships, includes one or more propellers of semi-submerged type, arranged with a partial immersion of the sole bottom blades and with the top blades emerged, regardless of the state of motion and the trim of the craft. The propulsion system allows, employed power being equal, a higher propulsion efficiency and allows to keep the driveline of the propellers entirely above water level, wherein the semi-submerged propellers are arranged at the transom, the ratio of diameter (D) or sum of diameters (Np×D) of the semi-submerged propellers to craft width (L) at the water line (3) is greater than 0.50.

Abstract: A propulsion system of displacement or semi-displacement ships, includes one or more propellers of semi-submerged type, arranged with a partial immersion of the sole bottom blades and with the top blades emerged, regardless of the state of motion and the trim of the craft. The propulsion system allows, employed power being equal, a higher propulsion efficiency and allows to keep the driveline of the propellers entirely above water level, wherein the semi-submerged propellers are arranged at the transom, the ratio of diameter (D) or sum of diameters (Np×D) of the semi-submerged propellers to craft width (L) at the water line (3) is greater than 0.50.

Abstract: A combined propulsion and steering system for motor boats with inboard engines comprises a propeller shaft projecting from the lower part of the transom of the boat and carrying a semi-submerged propeller screw which is enclosed by an arch-like deflector tunnel extending over and to the sides of the said propeller screw and turnable about a substantially vertical axis. The ratio (L/D) between the distance (L) from the rear part of the propeller screw to the lower rear part of the transom hull and the outer diameter (D) of the propeller screw lies between 0.8 and 1.8. There is also provided an engine exhaust gas duct, forwardly of said propeller screw.