Power steering issues
 

Been running my 35 Lightning for a bit and everything has been working flawlessly until this last week. Power (hydraulic) steering works perfect when I first fire up and run, but after about 20 mins of running it "fades" away more and more until no power steering at all. I stopped a few times to float and swim for a few hours and fired back up and sometimes it works somewhat (maybe 50%) and sometimes it's just as bad as when I stopped to float. Always works the next morning though. I checked the rams and found no damage and/or leaks. Fluid is at correct operating level. Maybe air in the line? Can you bleed the system somehow? Any ideas on what to check for?

Is belt slipping?

Not that I'm aware of but since you mentioned that, I just put new belts on a few weeks ago. I'll double check that to make sure they're tight. Those belts expand when they warm up?

Maybe do a full fluid change. Could be old/contaminated and getting weak with heat.

Had same issue. Check for leaks at the helm pump behind steering wheel in back panel. If the steering "chatters" a little and goes south, its that. Teague Marine in CA. supplied IMCO part to replace it. If its an Eaton pump (marked on outside), they dont make the part anymore. I looked.
Have to change it an "O" ring install and change the studs to metric in order to install. a PITA!!

Try the Pump filter also. It could be clogged with stuff. You may need to replace the filter anyway if contaminated.

Belts expand when warm IF they are NOT marine belts. Mercruiser belts stay where they are always (well almost always)