An oil pressure operated pump for marine steering gears includes a multiple piston oil pressure operated pump controlled by a steering wheel, a valve housing mounted under the pump, a bottom cover closing the valve, the valve housing and the cover each including channels, threaded holes for reciprocal fastening thereof, non-threaded bores for oil pressure connections, a valve set lodged in the valve housing for non-return and adjustment of oil flow, the valve set including a generally parallelepiped shaped tubular shell having a generally external square shape, a central tubular through-hole, and lathe-turned ducts, a double acting oil pressure cylinder including a shaft movable in the central tubular through-hole for controlling a direction of an engine or rudder of a boat, and valves for controlling fluid flow and thereby movement of the shaft.