There is some talks about converting mechanical steering to hydraulic specially for the I/O;
There is some infos that I think will be appreciate:
Most popular (Mercruiser):
Power Assist steering =
Power steering pump that is operated by the engine power pump which moves the Mercruiser power cylinder (not the Teleflex cylinder) . Cylinder required HC5328-3 to work with a SeaStar Helm pump and lines. You will have a hydraulic power assist steering, meaning, a hydraulic helm pump (HH5271-3), two steering lines, that run down to a power assist cylinder (HC5328) which in turn screws into the Mercruiser power assist cylinder (Mercruiser part) that is run from the power pump and this Mercruiser cylinder is connected directly to the drive.
Non power assist steering =
No power pump and/or power steering cylinder (no Mercruiser cylinder on board, no power pump) requires manual Hydraulic cylinder # HC5332. This means that all that you will have is a helm pump (at the steering wheel), two steering lines, going to a steering cylinder attached directly to the outdrive (HC5332).
With no power assist you will be manually moving the steering wheel, meaning that there is no power assist.
Application guide: http://www.seastarsolutions.com/products/hydraulic-new/sterndrive-steering-new/