Abstract: In a servo steering system for motor boats comprising a steering wheel which mechanically acts on the position of a hydraulic control valve, and a rubber cylinder connected to a hydraulic power unit by way of the control valve, the control valve comprises an additional adjustment unit which is connected to an autopilot unit and is controllable by this latter. In this way both normal servo-assisted hand-steering and autopilot steering are made possible in a simple manner.

Abstract: A hydraulic control unit, particularly for switching-over a boat reversing gear comprises a pump unit (2) fed by a tank (5), a switchable rotary slide valve combination (8) connecting two control junctions (A, B) either to the working pressure system or to the tank (5), and a working pressure relief valve (11). The discharge (12) from the working pressure relief valve (11) is fed to a cooler (14) with after-connected lubrication points. In order to prevent fluctuation of the pressure controlled by the working pressure relief valve (11) as a result of retroaction from the lubricating system or cooler (14), the spring compartment (33) of the working pressure relief valve (11) is connected to the tank (5). To control the lubrication pressure, a lubrication pressure relief valve (15) is connected between the cooler (14) and the lubrication points, and relieves into the tank (5).