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Author Topic:   Oil Reservoir Drip?
momann posted 07-02-2006 06:39 PM ET (US)   Profile for momann   Send Email to momann  
I've just noticed that when my 2001 2-stroke Mercury Outboard is tilted all the way up, oil slowly drips out of the oil resevoir right by the cap. Is this a common problem? The O-Ring on my cap is intact and well lubricated, so I'm guessing that the problem is with the threads on the reservoir itself. Any thoughts?

Thanks in advance,


sosmerc posted 07-02-2006 09:45 PM ET (US)     Profile for sosmerc  Send Email to sosmerc     
You didn't say what horsepower or model, but even so, leaking caps have been a common problem. I think the cause is initially the cap gets over-tightened..and that screws up the dimensions of the neck. You might try cleaning the inner area of the neck as well as the cap assembly and o-ring. Remove and clean the o-ring and try installing it reversed from its initial position. Then tighten the cap just enough for it to be secure. Tilt the engine only as high as necessary to keep the lower unit out of the water...and don't fill the tank as much.
You can replace the tank for about $65.00, depending on the model.
momann posted 07-03-2006 08:00 AM ET (US)     Profile for momann  Send Email to momann     
Thanks for the reply. It's a 90 HP, (not optimax) 2-stroke, if that makes a difference. I will inspect the reservoir more thoroughly and consider replacing it.


fishgutz posted 07-04-2006 11:13 AM ET (US)     Profile for fishgutz  Send Email to fishgutz     
I have a 2000 Merc 75 2 stroke, essentially the same motor. My oil reservoir leaked too, same place. I believe overtightening the cap warped the yellow part of the cap ever so slightly and it leaked. I changed o-ring and added washers to no avail. A new cap did the trick. That was 3 years ago now. Just get a new cap (cheap, I think it was $9) and just tighten until snug. Check it often and DON'T fill the reservoir right to the top.
Hope that does the trick for you, too.
bsmotril posted 07-04-2006 11:30 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
The caps on the resevoirs are VERY prone to crack right at the right angle corner where the top of the cap meets the sides. This is usually from overtightening. Often the crack won't even be visible until the cap is tightened to the point where the lip of the resevoir spout bears against the inside of the top of the cap, and opens up the crack. Remove the cap, inspect it carefully on the inside under a bright light while holding the sides and pushing up on the center top of the cap from the inside. BillS

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