BUP

iTrader: (9)

Currently as well for these power trim systems Mercruiser states "Approved Power Trim Fluids"

power trim & steering fluid - their brand

SAE engine oil 10W-30

SAE engine oil 10W-40

Again this is for current Mercruiser pwr trim systems straight out of OEM Mercruiser. I just looked it up FYI.

the deep

iTrader: (8)

I suppose this means it's ok to run engine oil in the power steering pump also since both are hydraulic pumps . I have never put engine oil in any type of hydraulic pump and have had zero problems . Even if Merc recommends it I'm not buying it .

Shalom

iTrader: (2)

Well, for sure 20/50 is not one of the recommended fluids....Thanks guys for input...Looks like I will empty out whats in there and start from scratch. If changing the fluids don't work at least I will know that its something else and I try the next idea.. What ever that becomes.....No thoughts on a possible seal sucking in air?

4bus

iTrader: (4)

Merc recommends engine oil because hydraulic oil is extremely hygroscopic (absorbs water like a beach towel). Did you know the brake guild in your car (sealed) in a normal non marine environment lasts only about 2 years? After that it is so water bound it starts to corriod internal brake parts, yes most calipers fail internal from neglected brake fuild. How long do you think think that hydraulic guild lasts in a marine environment on an open vent system?

The 10w30 works just fine, the system was designed for it. The 10w30 offers corrosion and moisture protection your hydraulic fluid can't.

His aerating issues has nothing to do with the oil he is running. My guess is he still has a leak, ok the return side, that is sucking air and puking fluid.

BUP

iTrader: (9)

His problem could be in the valve body as well but really not knowing what he has for a trim unit on a 1976 is a guess at this point. Is it the stock unit or changed out at certain timeframe or an aftermarket unit. Who knows. I think you might have the square body trim motor mounted to the old style reservoir. The Prestolite unit ? Mercruiser also has tests with a duel pressure gauge to determine problems for pressures and restrictions.

Also all Mercruiser trim units need to vent the air that's builds up out, so the correct cap is important so that unit vents properly. Like I said as you said you had the yellow cap but did it have the vent pinhole on the top. Very important the hole needs to be free & clear to vent, The later caps vented in the threads which also were junk because they did not stay screwed down tight and leak fluid out in rough water running. The newest caps are the best - they vent with a small sponge type filter as well.

Also after filling the trim pump full with fluid Merc recommends cycling the trim completely up & down a min of 10 times to bleed the air. The trim fluid will build foam from trimming a couple of cycles regardless.

Also make sure you just use the cap for the trim reservoir and do not have the red shipping cap still in there as well. Seen that a zillion times as the boat dealer newer removed it after the boat was transported to his dealership.

the deep

iTrader: (8)

I use only synthetic hydraulic fluids which do a much better job of holding any moisture in suspension . I have converted a couple braking systems to DOT 5 , including my boat trailer , with great success . You do what you want I will do what has served me well . Merc also wants us to use only their oil and filters in our engines too yet not too many do that either . And with that I withdraw from the conversation . JATOT

Shalom

iTrader: (2)

Thanks for the info guys... I have Oildyne pumps......I have the new caps ordered....."Also after filling the trim pump full with fluid Merc recommends cycling the trim completely up & down a min of 10 times to bleed the air.

The trim fluid will build foam from trimming a couple of cycles regardless.

I only cycled 3 times and stopped because of the foaming.......I should have kept cycling to get all the rest of the air out.....

OK .... After additional thoughts from you guys I have thought about what may have happened...I took may boat out in very rough conditions and ran the crap out of it... It was a blast... However... after the run.. I noticed oil in my bilge....After much investigation I determined that it came from this trim reservoir...."CAP LEAKING">>> which made it low and sucked in air.....l added fluid and started cycling it and it foam out.....MAYBE...no real problem at all...New cap and cycle the crap out of it to insure all air is out and try again... Thoughts....

Black Baja

iTrader: (2)

5w30 valvoline in all my pumps cause that's what I had laying around and I have no issues...

Shalom

iTrader: (2)

I just want to thank you for your comment as well.... I have posted a few times about potential issues... and was on the wrong side of the conversation.. Well as it seemed anyway...But later found out differently... When I started this post.. I had no clue as what the problem was.. And with your comments brought additional comments and now I have a few places to go....which I didn't when I started....So thank you and never stop posting a thought... It just made help lead to the answer.. which I believe is the case now... I do understand brake fluid/hydraulics and moisture issues and I also understand what you are saying too. They are all part of my equation to resolve my issue... Thank you for your comments....Russell

the deep

iTrader: (8)

You my friend are quite welcome .