5w-20 motor oil in the trim pump????

[RRitt]

Re: 5w-20 motor oil in the trim pump????

Then use the mercury fluid with exception of Force and some early sterndrive I/O using prestolite pump as pictured below. Prestolite systems with round valve bodies can buck if the fluid is too thin. IF your pump looks similar to attached picture then do not use anything except 30w non detergent motor oil.

You can mix dex3, TF, and H.O. I suspect the official mercury fluid is probably just iso32 H.O. repackaged into something less than a 5 gallon bucket. ISO32 is the best universal choice for warm weather hydraulics, AW32 for cold weather hydraulics, and tractor fluid for vehicles with shared transmission/hydraulic reservoirs. ISO32 has the best shearing, moisture, sealing, and rubber protection properties. AW32 is a variation of iso32 engineered to stay thin in colder climates. Tractor fluid is and ATF engineered to serve dual duty as both transmission fluid and hydraulic fluid for attachments. Marine trim systems see such infrequent use that it does not matter much. Just avoid detergents above 1200psi. You should be able to find trim operating pressure in manual since it is usually part of pressure testing.

 

[HT32BSX115]

Re: 5w-20 motor oil in the trim pump????

This is right off of Mercury's website:

MerCruiser Maintenance FAQs | Storage & Maintenance MerCruiser FAQs | Mercury Marine


What type of fluid should I use in my power trim system?
Mercury/Quicksilver Power Trim and Steering Fluid ? part # 92-858074K01


They may have recommended many different types of oils and fluids in the past but this what they are recommending now for ALL their power trim systems regardless of age.

This should not be very surprising since they sell it. (at a profit , I might add)

 

[tazrig]

Re: 5w-20 motor oil in the trim pump????

This should not be very surprising since they sell it. (at a profit , I might add)

I hope they sell it at a profit, that's what businesses are supposed to do. They also have a bunch of highly trained engineers who figure out what works best and have the company buy and recommend that product until they find something that works better and then they switch to recommending and selling that product. The engineers have every incentive to select the best product for their engines and pumps. The longer they last the better the reputation of the company and the more people will buy their product and the safer the engineers job becomes. I don't know about you but I'm very happy paying for their "profit" (as apposed to any other companies profit) so they can do all the testing for me and give me the bottom line on which product they find works the best in their engines of which I own a couple.

 

[HT32BSX115]

Re: 5w-20 motor oil in the trim pump????

I hope they sell it at a profit, that's what businesses are supposed to do.

As it should be. And I mean that!

 

[RRitt]

Re: 5w-20 motor oil in the trim pump????

well, speak of the devil.

I just rebuilt a 75HP 1996 Mercury trim system today. It was bleeding down. When I drained the fluid it came out looking like used motor oil. That is from the motor oil detergent dissolving the rubber and giving the oil a black tint. This system was not heavily used and would have gone another 6-8 years. Except that somebody somewhere put in the wrong fluid.

 

[elkhunter338]

Re: 5w-20 motor oil in the trim pump????

My manual says for 1964-1995 use 10-30 or 10-40 engine oil.

 

[Don S]

Re: 5w-20 motor oil in the trim pump????

well, speak of the devil.

I just rebuilt a 75HP 1996 Mercury trim system today. It was bleeding down. When I drained the fluid it came out looking like used motor oil. That is from the motor oil detergent dissolving the rubber and giving the oil a black tint. This system was not heavily used and would have gone another 6-8 years. Except that somebody somewhere put in the wrong fluid.

Believe it or not, outboards and IO's have different trim systems. So don't compare your OB to the IO questions.
The Merc outboards (like your 96 75horse) uses ATF as a replacement for the OEM trim fluid (Look at the manual), but the Mercruisers recommend 10W30 motor oil in the pumps today including the later pumps (1982 and newer) which call for 10W30 in the manual. These are the same exact pump as the OP has on his 73. Just newer ratings on the oil used.

 

[RRitt]

Re: 5w-20 motor oil in the trim pump????

it's a matter of PSI and which type of rubber used Don. Above a certain PSI motor oils and dextron will damage the rubber. It doesn't matter if it is a forklift, a trim system, or a roadgrader. In general under 1000psi use anything you want. Heck, vegetable oil would probably be just fine too. Under 1600-1800 psi dex3 is a great choice due to easy handling and low foaming. above 1800psi iso32 or aw32 should be the choice regardless of whatever mercury says. Mercury is not perfect. They have sold more than one product that could have gone 20-25 years but ended up self destructing after 10.

 

[Don S]

Re: 5w-20 motor oil in the trim pump????

:facepalm: :facepalm: