Mercury 25HP Leaking oil

F

firecan

Cadet
Joined
Apr 28, 2007
Messages
7
I started my 25Hp Mercury 2 stroke a couple days ago. After leaving it for a couple days I went back today to ove it off its stand and onto my boat and noticed a pool of black oil under it (had to be lower unit oil). I removed the prop and saw a trickle of oil coming from the seal where the prop shaft goes into the lower unit. Can anyone tell me if this is hard to replace as I just see a metal plate which looks to hold the seal in place, and is it as simple as removing that plate and replacing the seal and then putting the plate back in place.
 
achris

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Re: Mercury 25HP Leaking oil

If the oil you saw is jet black, then it is most likely exhaust 2 stroke oil and nothing to worry about. Check the oil in the gear housing, it should be a clear honey colour.

Chris...........
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Mercury 25HP Leaking oil

If you have OLD Hi Performance gear lube in there, it may also be black, or look black while it's on something.
If you suspect it from the lower unit, drain the gear lube (It may need it anyway if it's black) then do a pressure test to about 12 psi. Use a spay bottle with water and a LITTLE dish liquid. It will blow bubbles where the leak is.
 
F

firecan

Cadet
Joined
Apr 28, 2007
Messages
7
Re: Mercury 25HP Leaking oil

Thnaks alot for the advice. Just from the amount I don't think it's two stroke oil. I will drain it and do a pressure test on it and try finding the leak.
 
H

Harker

Chief Petty Officer
Joined
Sep 21, 2003
Messages
452
Re: Mercury 25HP Leaking oil

Stick your finger in it and smell it, if it smells like gas it is just unburned crud from the exaust housing....if it smells like brake fluid, it is probably lower unit oil.
 
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