Abstract: A controllable pitch propeller, particularly for a boat drive, has a driven rotating hub and adjustable propeller blades positioned thereon. An adjustment device is provided, having an adjustment ring that can move axially and which has adjustment bars attached to it for adjustment of the propeller blades. At least one continuous waste gas channel is positioned in the hub. In order to relieve the hub of external adjustment forces, the adjustment ring is constructed as a cylinder piston which is movably axially positioned in a cylinder chamber of the hub, and which can be acted upon hydraulically on both sides.

Abstract: A marine vessel having a propeller tunnel possessing a flow-favorable cross-sectional configuration following the flow lines of the water. Within the propeller tunnel there is mounted a propeller essentially throughout one-half of its circumference. An adjustable control plate can be extended in order to detach the flow of the water from the surface of the tunnel during rapid travel of the marine vessel. In this case, the propeller functions as a partially immersed propeller at a high rotational speed. There can be provided a control device which adjusts the control plate as a function of the rotational speed range within which the propeller operates. The propeller can be an adjustable propeller conjointly adjustable with the control plate.