power trim works fine but fluid appears milky

[Mursenick]

My 1993 mercury power trim unit works great. I just purchased the boat and decided to check all the fluids before boating season. I noticed that the power trim fluid appeared milky so i decided to pump it out. I put new fluid in and cycled the system a couple of times and fluid appeared milky again. After several times of changing and cycling the fluid appears the same. I contacted the local marina and the mechanic gave me instructions on what to do. I bought a whole gallon of dextron ii trans fluid and cycled changed, cycled changed and now it looks like strawberry milk. Mechanic said if I cant get it clean then it may have to be taken down and rebuilt to properly clean it. The fluid feels that it has a good consistency and the unit holds pressure well and operates perfectly, just looks milky. The advice I need is whether I should leave well enough alone and dont fix it unless its broke, or take it and have it rebuilt. The boat and motor are in like new condition and I plan to keep it a long time. Rebuild is rougly 400 bucks, new trim pump 896 bucks, but if it works fine its hard to convince the old lady it needs to be seen about. Any advice would be appreciated very much!!

 

[aussieflash]

Re: power trim works fine but fluid appears milky

Tilt to full up and check top of each ram for any leaks via cap seals,especially main ram seals.Ive seen a few of them completely gone and hanging at top of piston rod.If good leave up over night to see if holding position.If still good and it holds trim position while underway then dont waste your $$$.Have a closer look at fluid and make sure the milky look is not just tiny air bubbles.A photo will help.

 

[Texasmark]

Re: power trim works fine but fluid appears milky

Let the boat sit for a week and before you push the trim button again, check the fluid. First of all you have to have a source for "milk" in oil caused by water. On a lower unit, if it is truly water, it is because there is a leak and it sits submerged. PTT has no connection to water so there is no source for contamination. However, pump hyd fluid, by whatever name you choose, agitates the molecules by the pumping process, and in short introduces air which makes the fluids look milky when they really aren't. It's just the bubbles in the fluid as a result of running the pump.

By letting it sit for a week, the bubbles can dissipate and you will get your real answer; but you already have it....it's not water.

Butttttt there is one possible caveat and that is does your pump/piston sit under water in a marina or such; transom top close to the water line?

HTH,
Mark

 

[Mursenick]

Re: power trim works fine but fluid appears milky

Thanks very much for the replies. I checked the exterior of the pump and from what I can tell no leaky seals or anything. i forgot to mention that the o ring on the fill cap was the wrong size. The way I noticed this is I saw a little leakage at the bottom of the cap ( about a capfull ) . I replaced with the right size o ring and did all the things as stated above . The boat is stored in my garage when not in use so it is not in water unless im am spending time at the lake. I will try and leave it trimmed up and check it in a few days to see if all the air has settled and to make sure it holds good pressure. I will also try to post a pic of the fluid. Thanks guys

 

[RRitt]

Re: power trim works fine but fluid appears milky

you should be okay. your trim system is known to split like a pipe during really hard freezes if it has water in it. But Alabama should be far enough south that this isn't a problem.