Big Block Billy

A good friend of mine has a 175 Ocean pro outboard with a trim pump malfunction. There may be a problem with the hydraulics like a seal or a bad check valve. He had someone put a new motor on it and had the same problem. The whole unit is off the boat. He says it does whatever it wants to do and dosen't hold. Should I take it apart and fix it for him ? He took the unit off and then told me about the problem . Are they similar to older outboards, Mercs. and the hydrauilic system on Merc. I/o's ?
I usually stay far away from outboards.
Any help would be appreciated. Thanks, BBB