hydraulic steering device for outboard motors having an end for fastening to transoms of watercrafts . the motor / propeller assembly is mounted on the end to rotate about a substantially vertical steering axis . a closed hydraulic circuit has at least one pump driven by steering unit and at least one double - acting cylinder which is slideably fitted on at least one coaxial rod . the rod sealingly projects out of a cylinder head and carries a separating piston which divides the cylinder into two variable volume chambers . at least one of the inlets / outlets of at least one of the two chambers is formed by the at least one rod . the rod has an axial hole extending from its outer end to one or more ports for communication with corresponding chambers of the cylinder . the ports are arranged to be adjacent to the piston side turned toward the cylinder head from where the rod projects .