Hynautic hydraulic steering.

I'm taking a VERY educated guess here as I'm not looking at the electric motor, but 99% sure it is accurate. The electric motor would be the autopilot pump and that is what the autopilot uses to steer the boat left or right. When the autopilot is not engaged, the motor does not run and has no use.

Your steering system is not power steering. Cabo put power assisted steering on 40' Cabo's and above generally. These utilized a power steering pump that was generally mounted on the port engine. Your system is simply hydraulic and either steering station is the "pump" and you turning the wheel is what moves fluid in either direction. The system utilizes the resevoir which should be 1/2-2/3 full (it should have sight glasses along the side of the body or a clear plastic tube that runs next to the canister to see the fluid level) and then pressurized with air between 20-30 PSI, and you can use a bicycle pump to pump it up. The system uses Seastar hydraulic steering fluid, but you can also use ATF transmission fluid or AW 32 in a pinch (or AW 46 but would make steering a little stiffer). If you have air in the lines, which the steering will be a little skippy (tension turning the wheel), the easiest way to bleed air out of the lines is to make sure you have enough air pressure and fluid in the resevoir and then crack the hydraulic hoses behind the tower steering station enough that solid fluid comes out. Do not take them off. Any air generally works it's way up to the highest station.

Will this help you ?

http://cworthy.net/boat/documents/Hynautic Steering Installation and Operators Maunal.pdf

It's possible. I usually fill the system to 35-40 psi, then when you remove the bicycle fitting you lose a little, then I press down on the shrader valve to get it to 30 psi.

I've always kept the psi as low as possible where it still does the job it's intended to do. I fill mine up to 30 psi if the tower loses steering so I can bleed the tower station, then lower the psi to 10. I leave it at 10 and have no issues for a decade. If you leave it higher then it's more likely to leak; no need for more pressure if the steering is good.

Just a guy who owns a boat, but for me I run my systems at the recommended pressures. If they leak at those operating pressures somethings wrong and you should fix it. Dumbing down the system, imo, only leads to a bigger failure when you least need it. In this example , you would have no ability to bleed the air down to a get home with just a drip.

If that works for you then run with it! As a mechanic at Viking's south yard one of my primary responsibilities was steering system troubleshooting, R&R parts and proving the system. Many captains told me they run the pressure lower than the listed simply for the reasons I spoke of. Experience keeps a dear school and we all have slightly different lessons- but if they get us to the same place who's to argue?

Really the only thing the pressure does is keep air from entering the hydraulic system. 1 psi of air pressure would work even. Both ways work. I prefer to keep my air pressure higher when I fill it, but as with anything with air pressure in it, over time the air pressure will slowly leak out. I usually fill to 30 psi, then let it get down to 15 psi, sometimes even 12 psi to add (over the course of a few months depending on the boat). I do prefer it higher so if you have a very slow leak there's more time until it all leaks out. But if you have no leak 10 psi would be ok too really.

I think the Hynautic uses higher air pressure to actually push the actuators. Hynautic engine controls it's recommended to have 75-85 psi in the expansion tank.

How's that work?

Bueller? Bueller?

You have fluid at 75 psi at the helm control, so when you push the lever from neutral to fwd/reverse it assists the pressure you're using to move the fluid (pump it so to speak) foward or aft at the actuator.