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).