LU Screw seal

[aarongreen123]

noticed that the top lower unit screw had milky oil leaking from it on my 84 Merc 90 OB. Figured it didn't make sense to start worrying about other seals as long as there was so much oil leaking out from the vent screw for the gear oil. I took the gear oil out, white as the pure driven snow oddly enough. Attached is a pic of two new screw seals and the two old ones. Is this what happens to the old ones when they wear out? Did this guy use the wrong seals? Am i now using the wrong ones? I had the parts guy triple check but who knows....the old ones look thicker to me by a lot, and i can tell you that the new ones fit on the screws much more loosely. Old ones on the right. Nothin leaking now at least.

 

[Texasmark]

Re: LU Screw seal

If water in the oil it is usually chocolate to yellow depending on how much water. If using Lubriplate Marine it could be white grease. Merc lower unit lube is blue-black and Pennzoil is honey colored and translucent, not milky.

I don't know which is which, but I would use the blue OEM Merc washer that fits the shaft of the screw best. Also, if your lower screw isn't equipped with a magnet, get one. It picks up the little metal particles that are a natural result of operating the engine.

Mark

 

[aarongreen123]

Re: LU Screw seal

i drained it and replaced with the green Sierra gear lube, is that ok to use in a merc LU?

 

[Chris1956]

Re: LU Screw seal

Any color is fine, Mercs are colorblind. Seriously, if the gear lube you used is made for marine mechanical shift outboards, you put in the right stuff.

Run for a few hours, no more and recheck gear lube for water infiltration. If you find it, I would recommend you replace waterpump base since it will have a new driveshaft and waterpump base seal. Obviously you need to clean and lube driveshaft before installling new pump base.

 

[aarongreen123]

Re: LU Screw seal

thank you very much Chris i appreciate your help. just to clarify, are there any circumstances where white gear oil coming out could be considered normal?

 

[Chris1956]

Re: LU Screw seal

Only if you put white gear oil into the gearcase. Hence the test with some known gear oil....

 

[aarongreen123]

Re: LU Screw seal

ok cool, i'm thinkin that thats not what happened here. The gent did mention that he hadn't replaced the impeller in 5 years or so, so i might as well replace parts around that when i get in there. When you say the water pump base you are referal to the metal plate the the house sits on correct? or are you refering the housing as well.?

 

[Maxz695]

Re: LU Screw seal

There is a O ring that seals the pump base housing to the lower case that prevents water intrusion and a seal in the pump base as well that seals the drive shaft

 

[JB]

Re: LU Screw seal

Look at the plug gaskets in your pix, Aaron. See that the "used" ones are squashed (crushed) bigger?? That is because using them ONE TIME uses them up. Never re-use them. They are one use gaskets, not washers.

Failure to use new gaskets on the Drain/Fill and Vent plugs after every service is the most common cause of water intrusion in the gearcase.

You fixed your problem with your first move.

 

[aarongreen123]

Re: LU Screw seal

JB
I was wondering if that was the case, thanks for the clarification. i am crossing my fingers that that was why the gear oil was white.