Abstract: Boat propeller drive unit with an underwater housing (5), which is solidly joined to a boat hull and has pulling propellers (15, 16) on the forward facing side of the housing. At the aft edge of the underwater housing, a rudder is mounted, comprising a first rudder blade (22a) mounted in the underwater housing and a second rudder blade (22c) mounted on the aft edge of the first rudder blade.

Abstract: Boat propeller drive unit with an underwater housing (5), which is solidly joined to a boat hull and has pulling propellers (15, 16) on the forward facing side of the housing. At the aft edge of the underwater housing, a rudder is mounted, comprising a first rudder blade (22a) mounted in the underwater housing and a second rudder blade (22c) mounted on the aft edge of the first rudder blade.

Abstract: The mounting of a thruster propeller unit in the bottom plating of a vessel is facilitated by the use of lifting lines, operable from within the vessel. Each line is made to pass a lock chamber adjacent to an opening in the bottom plating, outside the opening where the thruster propeller is to be fitted. The lock chamber includes a first, rigid tubular member, which is formed as the housing for a slide valve, as well as a second tubular member, which is resilient at least in the transverse direction. The two tubular members define a passage being substantially wider than the diameter of the lifting line. The second tubular member is at its top provided with a sealing sleeve which fits around the line. The locking chamber is connected to a source of compressed air, which makes it possible to maintain a pressure within the chamber balancing the pressure of the surrounding water.