2004 90hp lower unit

[TonyMe]

I have a 2004 Mercury 90elpto that the lower unit is losing oil. There are no signs of leaking oil anywhere and I pressure checked it and it went from 20.75lbs to 19.75 lbs in about 20hrs. Which seems pretty good to me. I have the lower unit off and I am planning on replacing all the seals and gaskets since before I bought the bought it sat for about 7-8 years. The lower unit works good. Looking for some thoughts of where and why it could be losing oil. All shaft busings seem nice and tight. There was almost no time on the motor.


When I fill the lower unit with the proper amount (approx. 22oz.) and I go run the motor once or twice and check the level nothing ever comes out the screw holes. I would remove the vent and fill hole plugs and tip the motor up all the way with the screws out and nothing comes out so it is confusing me. After you fill the lower unit and run it then check it a day later the oil level should still be at the vent or the fill plug right? I have a 9.9 Johnson and that one stays filled the the fill hole.

Thank You, Tony

 

[flyingscott]

You will need to check all your seals as you over pressured the lower unit you test them at 5-10 psi. How are you filling it do you fill it from the bottom hole.

 

[TonyMe]

Yes I fill it from the bottom hole. It is still holding at 19.75 psi over 24 hrs later. It didn't start pushing out of the seals until around 23 - 25 psi.

 

[flyingscott]

If you think your seals are good. The lube can only leave 2 ways through a seal or a crack.

 

[Faztbullet]

You need to preesure check it at 10psi max and also vacuum test it. They can pass pressure test and fail vac test.

 

[TonyMe]

Ok. The pressure test isn't helping since it is holding at 19.75 almost 48 hrs later. I will have to try and make a vucuum setup and try that way and see if that will help me fiqure this out.

After you fill the lower unit and run it the level should remain at the vent hole or fill hole correct?

Thanks, Tony

 

[TonyMe]

I replaced all gaskets and seals and everything looks, I checked it at 10 psi and everything is good. I did find 3 worn seals so I assume that's where I was losing the oil.

 

[Bayou Dave]

Glad you found the problem. Just keep an eye on it for a while.

 

[racerone]

Depending on what you use to fill the lower unit you can get air trapped in the oil.---Oil will show up at the top hole.----I then wait 1/2 hr with filler hooked into the lower hole.---This allows trapped air to work its way out.-----Then do a final top up .

 

[Texasmark]

You should have 2 vent holes. The manual procedure states that you open both vents, fill from the drain hole with the engine vertical until the front vent is venting a reasonable amount of oil and bubbles and close it off while continuing to pump oil into the drain hole and then the aft vent hole will ooze oil and bubbles and you insert that screw and tighten, then pull the fill tube and quickly insert that screw....new seals on all three screws.

If you have no other alternative or don't care to pursue it, just fill it and go out and have fun. Every so often, after the engine has been sitting without the prop or crankshaft being turned for at least 24 hours, ease out the drain plug and check for water or yellowing of the oil. If none you aren't leaking.

Especially in the winter with lots of slow running where the engine essentially stays cold, it's not uncommon to have oily resiudue from the fuel mix slobber all over the lower unit wherever it can get out. This is January!!!!!!!!!

 

[TonyMe]

Yep I was following the procedure above and rotating the prop 10 times after the oil came out of the first hole before I would fill it to the vent hole. I read that in a service manual. I will keep and eye on it once I start using it again in spring.

Thanks for the help, Tony