Water in the Lower Unit

[zippy83]

Hi All,

I have a 2021 Mercury proxs 200HP outboard, and during my last lower unit oil change I noticed slight amount of water in the lower unit. Since then I changed the drain and vent gaskets, filled it back up and put about 25 hours on it, and wanted to check the oil again and there was some water in there again..

what should I check for next? take off the lower unit and replace some seals?

 

[cyclops222]

I have never seen a separated oil like that.

 

[zippy83]

I have never seen a separated oil like that.

it is a very small amount Im guessing. here is what it looked like after it was all drained

 

[tpenfield]

Looks like Merc's High Performance gear lube . . . Emerald in color. Next steps are a pressure test of the LU. New seals may be in your future.

 

[zippy83]

Looks like Merc's High Performance gear lube . . . Emerald in color. Next steps are a pressure test of the LU. New seals may be in your future.

what seals are likely to go after 4 years of use? 250 hours...

 

[Chris1956]

Use the gear oil fitting on a bicycle pump to pressure test the gearcase. I would suspect the shiftshaft seal.

 

[tpenfield]

what seals are likely to go after 4 years of use? 250 hours...

what seals are likely to go after 4 years of use? 250 hours...

Yes, the short amount of time seems rather quick. You got the drive shaft seal and prop shaft seal . . . Might be another. The pressure test will tell the story ( as mentioned, not much pressure is needed)

 

[jimmbo]

First Seal to fail is usually the one under the Water Pump, and the pressurized water is pushed into the Gearcase.
Correction, the Seals that fail first are the ones on the Drain and Vent/Level Screws.
I would refill the Case with Oil, use new Gasket/Seal on the Drain/Vent Screws use it a few Times. Back at home, let it sit vertical for several hours/days, and crack the Drain screw and see what comes out.

 

[cyclops222]

Marina help causes some of these problems.

 

[Chris1956]

Gee, I would perform the pressure test. My inline 4/6 engines had the driveshaft seal fail most often. However, the newer V6 Merc has had two failed shift shaft seals, and the driveshaft seal has been fine.

 

[airshot]

Is there a possibility of internal sweating from all this heat and humidity ? Have saw that happen in the past. Doesn't appear to be that much is my reason for saying this. I would replace this oil and run it for a while then check it again. After a few changes, is there still signs of water ? Not sure there is enough water to blame a leaking seal just yet. But keeping an eye on it....yes !

 

[Chris1956]

Ideally all of the air is out of the gearcase, after you fill and seal it. Sweating would be non-existent.

 

[jimmbo]

Mercury used to want a bit of Air in the Gear Case to allow for Expansion of the Oil as it warmed up in use. The Filling Instructions said to Fill till it came out the Vent, then let a tablespoon or so, out the Drain Screw, before Closing it up. Liquids can't compress, and if there isn't any free space, they will force their way past the Seals

 

[Chris1956]

Jimmbo, You are correct. However, after you fill the gearcase, you remove the pump or tube and some gear oil spills out, giving some airspace. Also, when filling the gearcase, there are always a few bubbles that will pop, giving added airspace.

There is not (IMO) enough airspace to allow sweating of the gearcase.