I have in 4.3L Mercruiser inboard/outboard and my power steering is not working like it used to. Where I used to be able to turn the wheel with one finger I have found it now takes a lot more effort to turn the wheel (but much easier than with the engine off). I checked the power steering fluid and it is at the right level. I hadn't run the boat since last fall. Does this sound like I need a whole new power steering unit or something else?