Abstract: A hydraulic engine employs dual cylinders and pistons of different diameter connected end-to-end in collinear alignment. Fluid from a pressurized source drives the large piston to transmit power to a crankshaft. An electromagnetic actuator, controlled by a distributor, opens a control valve, admitting fluid to the large cylinder. A hydraulic actuator closes the control valve, shutting off fluid flow. The hydraulic actuator responds to pressure drop when the large piston uncovers an exhaust port. Fluid drains to a tank, and the cycle repeats. The small piston recirculates fluid from the tank to the source.