I noticed on the bottle of Merc trim oil, it said can be used for power steering.

Does this mean that automotive pwr steering fluid can be used in trim pumps They both seem to be about the same viscosity.

The trim pump works off a fluid. Water would work if it had some lubricating and anti-corrosion properties. I used 10w-30 in my pump and just recently replaced the pump. When I refilled the resevior I used the merc trim/ps fluid which was much thinner. Still seems to be working just fine.

Transmissions fluid in power steering, motor oil in trim pump

I've always used power steering fluid in the steering (stock steering) and 30w in the trim pump. Never had any issues with either.

Then agian, my chit never seems to run these days so maybe you don't want to take any advice from me?

I`ve never had to add fluid to my trim reservoir, but it looks like p/s fluid in there. My trim-tabs have a slow leak, and must be tpped off about once or twice per season. It says on reservoir to use Dexron II or similar automatic trans fluid...

If you boat in colder weather use the PS fluid, if not use 30 wt motor oil.

Well I put in a 10w 30 last night, I hope the detergent doesnt cause a problem. The pump seems like it has to "work a lot harder" now but it works

I'm thinking about pulling the merc fluid out of mine. There is a slight leak and I'm thinking that the thinner fluid is splashing around too much.