# 25 h.p. Mercury 2 stroke Leaking Oil



## Nailer639 (May 1, 2006)

Last fall I noticed that my motor was leaking oil. It was coming out from the center of the prop behind the nut. I went ahead and replaced the lower end oil and winterized it, and havn't checked it since but it seemed to only leak after I ran it. 
Is this possibly an easy fix for someone with decent mechanical skills? Or should I have a pro fix it if spring comes this year. Thanks.


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## MIKIE (Sep 14, 2004)

It might be unburned oil from the fuel mix in the exhaust ? Mike


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## KaGee (Sep 8, 2006)

Probably unburned oil. Gear oil will seldom visibly leak out, you just start getting a lot of water in the lower unit. Bad nylon washers on the fill and vent screws are just as liable to let water leak in. They should be replaced with each oil change.

The proper procedure would be to have the gear case pressure checked first. That will tell you or the mechanic if the seals are going bad. As for how hard of a job is it to do, that is subject to your mechanical skills and tools you have available. I have resealed lower units several times.


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## Net (Apr 10, 2004)

KaGee said:


> Bad nylon washers on the fill and vent screws are just as liable to let water leak in. They should be replaced with each oil change.


Keith, where do I find those nylon replacement washers? I tried searching Cabelas.com but not having much luck.


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## Muskeye (Apr 12, 2004)

Pull the prop to make sure you have not picked up fishing line that has affected your seal.


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## KaGee (Sep 8, 2006)

Net... I'll find them For ya when I get to my pc

Sent from my Sprint Samsung Galaxy S4 using Ohub Campfire mobile app


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## Nailer639 (May 1, 2006)

I have never replaced those nylon washers on the screws. That sounds like a good place to start. Thanks. 

I did have the prop off and greased it so not a fishing line problem. Thanks.


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## KaGee (Sep 8, 2006)

Net the store in Dundee used to carry them... don't know why they don't list them or make it hard to search for them on the web site.


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## Net (Apr 10, 2004)

No problem Keith....thanks for looking. I'll ask for them next time I'm at Paul's Marine in Delaware. They have a good parts dept there.


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## crappiedude (Mar 12, 2006)

MIKIE said:


> It might be unburned oil from the fuel mix in the exhaust ? Mike


I agree, I have a 94 Merc 40 hp that does this.


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## ebijack (Mar 31, 2013)

West marine or most any marina should have them. I believe even Wal-Mart has em.


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## Bad Bub (Jan 17, 2006)

Net said:


> Keith, where do I find those nylon replacement washers? I tried searching Cabelas.com but not having much luck.


I buy mine for my '04 merc from auto zone. You can also buy them from eBay, but shipping is a killer...

Sent from my DROID RAZR using Ohub Campfire mobile app


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## Dr J (Apr 10, 2011)

The Sierra part number is 18-4248-9 for OMC motors (Johnson & Evinrude); don't know about Merc. Cost is around $3.00 for 5 washers. Don't know why there are five; the motors use 2 per motor.


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## Insco (Apr 9, 2008)

Same reason that hotdogs come in packs of 8 and the buns in packs of 10


I may have that backwards.


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## Nailer639 (May 1, 2006)

I have 2 more questions about this topic. I don't want to beat a dead horse but...

1. If I replace those nylon washers on the drain and vent screws and the motor continues to leak, Should I focus on replacing what appeared to be some type of seal behind the prop. I think it has three screws. What is involved in changing that bad boy? Or is that the seal that you mentioned before Kagee with the pressure check?

2.If it is unburned engine oil coming out of the exhaust should I try to lean up the mix ever so slightly on the next fill up? Thanks

O.k more than 2 questions I guess.


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## MassillonBuckeye (May 3, 2010)

Net said:


> Keith, where do I find those nylon replacement washers? I tried searching Cabelas.com but not having much luck.


Pauls Marine will sell ya a few.


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