FishingisaScience

Merc Lower Unit Seals

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So during winterization I noticed the LU fluid was a nice dark green milk.  No shavings when I went through the fluid in more detail.  Now I know this color/texture is indicative of water intrusion, but how difficult a project is this?  I have rebuilt the carb and done frequent impellers on this boat, and completed VST and injector rebuild services on Yammies.  Youtube has not been my friend with figuring this one out!  Motor is a 2004 25hp 2 stroke.

 

If this is a mechanic job, any ballpark on cost?  Sorry for the long post!

Edited by FishingisaScience

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Any pictures of the lu oil. That merc stuff is green. l usually see some white foam on top when draining.   My suzk is a clear gold oil .

 

Oh that plug did any water come out first when you pulled out plug before you seen Any oil?

 

 

 

 

Edited by 757saltwater

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I have a 200 merc and i do get a little discoloring . I use the yellow plastic with the metal inside seals for the 2 plugs . The paper/gasket material ones i had problems with . 

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All LU oil that is contaminated with water will appear milky to some degree or another depending on the amount of water in it. Much like coffee reg., light etc. We don't want mocha oil.:beatin:

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No water when I first drained it.   It definitely looked like a melted mint frappe.  I tried to take a picture, and oily fingers couldn't unlock my screen.  Off to AutoZone for recycling it went.

 

As an aside, do any of the newer motors monitor lower unit temp similar to how a truck shows transmission temperature?  I could FLIR it after running in the spring--diagnosed some interesting motor issues for others with this little cameras!

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I think you’d have to wait a loooong time to see water come out of the drain since the water and oil emulsion doesn’t separate quickly. 

 

Have the unit unit pressure tested as a starting point. It can be something very simple such as the plug gaskets or the seal between the upper and lower units. 

 

Seals requiring removal of the guts might be better handled by a shop. 

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It’s where anyone looking for a let is going to start. 

 

The one time I had that  problem, the unit was pressurized through a plug hole and no leak was found indicating that the leak was at that plug gasket. 

 

It was a 50 cent repair. 

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I used to winterize my outboards myself and one time I had a bad shift shift seal, not a major problem but other times it was the plug gaskets which I found by doing pressure and vacuum test. With my present boat I have the service done and at first I was resistant as to why the tech always installed new plug gaskets but today I understand it’s well worth the cost. 

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