I have a combination hyrdraulic/mechanical system which works well. Originally it was B&G Helmstar but the electronics gave up the ghost so I replaced them with Raymarne S1 electronics, using the B&G pump and ram assembly. With this type of arrangement a way has to be found to engage and disengage the hydraulics. The B&G pump/ram assembly contains a solenoid valve which, when powered up, engages the ram. I run this from the "clutch" supply on the Raymarine computer. When powered off the valve allows the oil to bypass from one end of the ram to the other, enabling the mechanical steering to work. So to enage the ram I just turn on the pilot. The only problem is that the wheel moves each time the pilot operates. My last boat was all hydraulic with wheel steering pump with check valves. No need for a solenoid and when the pilot was on the wheel did not move. I think this sytem was better as the system locked the rudder if I let go of the wheel which allowed me to attend to other jobs around the cockpit without the boat wandering off course.