Sounds like the helm to me, too.

There's no signs of an external leak at the helm but haven't popped the cover off yet to check further. Is there anything specific I should be looking for when I do take the cover off?

When the problem showed up last year was it after you added fluid? Just wondering if you did add fluid if what you added is not compatible with what was in there? I know certain greases cant be mixed. They go from grease to soup. Might just need a flush and refill?

I don't know. It has been 40 years since I was in hydraulics/pneumatics class. I do know they have a series of valves and vanes, it is a pretty complicated design, and you likely would be better off to get a replacement. I would call IMCO to get the correct replacement. I really doubt they make it, they most likely buy it from Parker Hanifin. The part number is probably on yours and you can get them from any hydraulic supply house. They are a very common steering pump on fork lifts etc.

Thanks for all of the suggestions everyone! Took the boat to the ROPA Battleship Run this weekend. Back it into the water it wouldn't start. Threw in 2 new battery's and still no luck. Looks like I have a few new issues to figure out before coming back to the steering. B.O.A.T

Bring this thread back around as I now have more questions then answers on my steering issues. Turns out I have a latham marine steering system not imco. Once I figure out how to change the thread title I will. So I was still having issues where the steering would bleed all of the air out and be rock solid at the drive no movement at all side to side. After 12 hours or so there would be about an inch of play and it would progressively get worse as time goes on. Using some leak finder dye I figured out the bottom seal on the reseviour was leaking so I replaced the seal. Bled the whole system again and am still having issue. I can bled the air out but once the engine sits not running it looses pressure. I pulled my power steering pump off and noticed the inlet to the pump is a very loose push in AN fitting. Is there a reason the pump inlets aren't threaded? I understand there is just head pressure from the reseviour on that side of the pump but could a very loose fitting be causing air into the system?

https://cimg3.ibsrv.net/gimg/www.off...8882287319.jpg
https://cimg7.ibsrv.net/gimg/www.off...0d66f772e4.jpg

At the very least I would expect an o ring on that fitting. Would be a little tricky to machine the groove but possible.

The stock mercury version of that pump has a steel tube pressed in there and uses a hose & clamp