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Ted G.
Ted G., Rigger, Diagnostician
Category: Boat
Satisfied Customers: 6089
Experience:  40 years boating, Safe boating instruct., Offshore Race promoter, Failure Analysis, Expert Witness
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I have a 1991 mercruiser Alfa 1 and have a issue with the trim.

Customer Question

I have a 1991 mercruiser Alfa 1 and have a issue with the trim. When I raise the leg its fine but when I lower the leg my oil becomes all milky with air. I had a seeping cylinder so I replaced the cylinders and still have the same issue. The more I use it, it will stop raising my leg all the way. I raise the leg and lower it and its milky, let the oil clear for about a hour and do it again and get the same result. Looking at replacing the pump?
Submitted: 1 year ago.
Category: Boat
Expert:  Ted G. replied 1 year ago.
Actually if you had a leak in one of the cylinders it is likely that the milkiness is water in the oil. If oil leaked out it is likely water leaked in too. But all that may be necessary is to flush the system with clean oil, possibly more than once. Just get a catch pan and remove the lines from one end and then the other while operating the trim buttons so fluid comes out. When the fluid is all clean at each line you should be good, just make sure the fluid never runs out or it can damage the pump.
Customer: replied 1 year ago.

Would water clear out of the oil within like 30 minutes? When I look into the fill hole the oil is clear, I raise the leg up and its still clear, I lower the leg and within seconds of hitting the down button you see a white slick come over the oil. About 30 minutes it becomes clear again. I have some kind of biodegradable oil in it now but it is like $20 a liter, I read all sorts on line what kind of oil should I use?

Customer: replied 1 year ago.

Would water clear out of the oil within like 30 minutes? When I look into the fill hole the oil is clear, I raise the leg up and its still clear, I lower the leg and within seconds of hitting the down button you see a white slick come over the oil. About 30 minutes it becomes clear again. I have some kind of biodegradable oil in now but it is like $20 a liter, I read all sorts on line what kind of oil should I use?

Expert:  Ted G. replied 1 year ago.
It is probably just separating and sitting on the bottom. Whatever fluid you have in their is not hydrophilic so the water mixes as it moves through the piping then separates to the bottom, then gets pushed back in the piping as you raise the leg. You are seeing it come back out of the rams when you lower them. You can use straight 30 W oil or transmission fluid. Since you may run at cooler temps I would use transmission fluid (cheapest you can find).
Customer: replied 1 year ago.

if I disconnect the line and bleed out the line how do I make sure there is nothing in the cylinders themself could you be a little bit more explaination on how to blead the two lines and cylinders

Expert:  Ted G. replied 1 year ago.
Here is the bleed procedure from the manual.
https://www.dropbox.com/s/h23246uvd7u5afl/trimout.JPG?dl=0
https://www.dropbox.com/s/ehpu9gmpfiqhrax/trimin.JPG?dl=0
Just don't let the fluid reservoir get empty while doing it.
Customer: replied 1 year ago.

okay I ran with the water idea, I took a suringe and took a sample from the very bottom of the tank and put it in a clear glass, no water, I lifted the leg and then lowered it and took a sample of the foam, put it in a clear glass and let it settle, no water...now what, back to a new pump again? I did take a picture and it settled completely oil

Expert:  Ted G. replied 1 year ago.
Okay, that could be caused by a restriction in one of the lines. Did you by any chance crimp one of them when you replaced the rams?
Customer: replied 1 year ago.

no , this problem all started last summer, i thought i could see a little bit of weeping on one ram so I replaced them both, and this problem still persists. I had the boat parked all winter with the leg up and it stayed up.

Expert:  Ted G. replied 1 year ago.
Alright, before we condemn the pump I would like to get either ATF or 30W motor oil into it. I'm not sure what that is in there but one thing about motor oil and ATF is they are formulated not to foam up. Yes, it is possible the pump vanes are worn and causing cavitation, but I have seen some very old, well used trim pumps and never saw them do that. I would really not want to spend your money needlessly on a new pump if it's not necessary. Sorry I led you on the whole water thing, but that is normally what makes the fluid cloudy, but I also have never seen fluid that looks like that, it almost looks like vegetable oil. (which is used in a lot of lower pressure hydraulic units BTW)
Customer: replied 1 year ago.

hoping to do your idea of changing the oil today

Expert:  Ted G. replied 1 year ago.
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