[willy]

MJ I'm not sure how it works, again I've only had contact with it once but the steering system for that engine does need the belt . At least that is what I was told by the guy who had it for years. Unless what happened on his boat is the power steering system died and he or someone before him decided to update the system and installed a aftermarket hydraulic system in it's place and the problem he is having now is related to that updated system.
The reason I say that is there would be no reason for a helm fill port on that older system, it should be mechanical to the power steering pump and the fill should be at the pump.
You need to look at the helm inside and see if you have a newer design hydraulic set up there if you do then you need to trouble shoot that and don't touch the disabled power steering pump on the engine