Abstract: An in-line power steering system for a marine vehicle having a propulsion unit, including a steering arm, to effect steering movement thereof about a steering axis, and an operator actuable steering helm. A first actuable steering member, such as a mechanical push-pull cable, is operably connected to the steering helm and actuated in response to steering actuation at the helm. A power steering assist unit, operably connected to the first steering member, comprising a hydraulic cylinder-piston assembly and hydraulic fluid source is interposed between the steering helm and the first actuable steering member and mounted remote from the propulsion unit, and further is hydraulically actuated in response to steering actuation at the steering helm. An actuator for regulating the flow of hydraulic fluid through the power steering assist unit is operably connected to the first actuable steering member.