A steering system for a boat, a marine vessel or the like, having an outboard motor with an underwater propeller and a removable fastening terminal at the hull, includes a steering control member, such as a steering wheel, a rudder bar or a rudder wheel, and an actuator that changes the orientation of the propeller by changing the angular position of the rotation axis thereof relative to the longitudinal axis of the boat. An intermediate framework, positioned between the stationary part of the boat and the fastening terminal of the engine, includes a housing for at least a portion of the drive assembly and/or of the actuator fastened to the intermediate framework.