Systems and steering actuators for steering outboard marine engines

A steering actuator is for steering an outboard marine engine about a steering axis. The steering actuator has a piston device and a valve device. Hydraulic actuation of the piston device causes the outboard marine engine to pivot about the steering axis. The valve device controls a flow of hydraulic fluid to the piston device to thereby hydraulically actuate the piston device. The valve device comprises a lead screw; a motor configured to rotate the lead screw in a first rotational direction and alternately in an opposite, second rotational direction; and a ball nut coupled to the lead screw such that rotation of the lead screw causes the ball nut to axially move along the lead screw, and wherein axial movement of the ball nut along the lead screw actuates the valve device, which thereby actuates the piston device to steer the outboard marine engine.