A power steering system for a watercraft includes an electromechanical rotary actuator mounted within a cylindrical housing. The electromechanical rotary actuator includes a motor and a gearing system. The housing, along with a stern bracket and an output flange, are sized and arranged to permit steering movements and trim/tilt movements of an outboard motor. The power steering system may include one or more of a redundant linear actuator, a trim/tilt mechanism, and a control system.