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Author Topic:   Mercury Leaking Oil When Tilted

j_anicker posted 09-04-2003 01:50 PM ET (US)
I have a 1995 Mercury 90-HP on my Outrage 17. When the motor is tilted fully up, which I like to do when moored, the two-cycle oil leaks from the engine. It appears that the leak is at the fill port. I can't believe that it doesn't seal fully.
Has anyone else had this problem? Is there a solution? Can the motor only be partially tilted, or is there a fix to the filler door seal?
FISHNFF posted 09-04-2003 02:15 PM ET (US)
I had a 1996 Mercury 75, and had the same leak. It got so bad that I sold the engine. I tried replacing the rubber O-ring at the fill port. Worked for a few months. The only thing I could think of is that the filler neck got out of round. I was going to replace the oil tank, but a deal came along on a Mercury 90 Fourstroke.
The oil leaking did not occur for the first couple of years. After that, on occasions, I would come back to the marina and find an oil slick around my boat. The transom well would be blue with oil. Opening the cowling, there would be oil saturating the foam on the inside front.
Here's what I found:
Tightening the oil cap snugly, not tight, made the best seal.
Changing the O-ring helped for a while. I even found a soft hollow O-ring, and that only helped a little.
Leaving the tank 1/2 full worked. On a long trip I would just fill it up before going.
I would tighten, tilt, and check for leaks over and over. Sometimes it would take 5 or 6 tries. Sometimes I would give up and just leave the motor down.
I'm sorry I don't have a definitive answer. I tried for 2 years, and could not make sense of it. Sometimes it would be fine. I just think it is a poor design. My Yamaha had a snap in plug, and never leaked.
If you have any other questions, you can e-mail me.

FISHNFF
j_anicker posted 09-04-2003 04:06 PM ET (US)
Thanks FISHNFF, you describe my problem exactly.
On my engine, however, the filler sounds a little different. I have a hinged snap shut rectangular "door", so there's no way to adjust how tight it seals. Seems like it's either going to be snug or loose, depending on the state of the seal. It's also not an o-ring, but rather, a closed-cell like foam that covers the whole inside of the cap.
I'll see if that seal can be replaced...
John O posted 09-04-2003 04:19 PM ET (US)
Same leak problem on my Mercury 2001 75hp 2 stroke. This is a new motor. I found that I must fill just above the "ADD 1 QUART" level to minimize spilliage. I do see some drops from time to time but I think it is from the carbs.
newt posted 09-04-2003 10:02 PM ET (US)
Same problem on a 2003 Mercury 90 Classic (2-stroke) - since motor was new. I am too lazy to pursue a remedy.
whalernut posted 09-05-2003 03:55 PM ET (US)
I am not trying to be rude or anything, but is there a way you could convert them to 50/50 mix and mix the oil and gas in the tank? I really like the simplicity of that. I hope you all work out the leaky problem, and if you find out a solution, please post the remedy :-) Jack.
j_anicker posted 09-05-2003 05:06 PM ET (US)
It might be possible to convert the engine to non-injection and use pre-mix. Not sure...
However, I did find a conversion kit for the oil tank from Mecury, about $199, that moves the tank off the engine to a pressurized tank that can tuck away in the lazerette. Link below:
http://www.mercurypartsexpress.com/PartsExpress/ProductSelection/Accessories/getProductGroup.asp?CID=163160187068235063274&lvlOneKey=35&key=1400&level=3&store=Accessories
Kind of a spendy fix to an obvious design flaw! I'm going to start with a new gasket and only keep the tank 1/2 full and see how it goes.
Thanks for the help!
newt posted 09-05-2003 10:03 PM ET (US)
The leaking oil doesn't bother me enough to convert to pre-mix, and I find the on-engine oil tank is handy. Simple green takes the oil off easily enough also.

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Author	Topic: Mercury Leaking Oil When Tilted
j_anicker	posted 09-04-2003 01:50 PM ET (US) I have a 1995 Mercury 90-HP on my Outrage 17. When the motor is tilted fully up, which I like to do when moored, the two-cycle oil leaks from the engine. It appears that the leak is at the fill port. I can't believe that it doesn't seal fully. Has anyone else had this problem? Is there a solution? Can the motor only be partially tilted, or is there a fix to the filler door seal?
FISHNFF	posted 09-04-2003 02:15 PM ET (US) I had a 1996 Mercury 75, and had the same leak. It got so bad that I sold the engine. I tried replacing the rubber O-ring at the fill port. Worked for a few months. The only thing I could think of is that the filler neck got out of round. I was going to replace the oil tank, but a deal came along on a Mercury 90 Fourstroke. The oil leaking did not occur for the first couple of years. After that, on occasions, I would come back to the marina and find an oil slick around my boat. The transom well would be blue with oil. Opening the cowling, there would be oil saturating the foam on the inside front. Here's what I found: Tightening the oil cap snugly, not tight, made the best seal. Changing the O-ring helped for a while. I even found a soft hollow O-ring, and that only helped a little. Leaving the tank 1/2 full worked. On a long trip I would just fill it up before going. I would tighten, tilt, and check for leaks over and over. Sometimes it would take 5 or 6 tries. Sometimes I would give up and just leave the motor down. I'm sorry I don't have a definitive answer. I tried for 2 years, and could not make sense of it. Sometimes it would be fine. I just think it is a poor design. My Yamaha had a snap in plug, and never leaked. If you have any other questions, you can e-mail me. FISHNFF
j_anicker	posted 09-04-2003 04:06 PM ET (US) Thanks FISHNFF, you describe my problem exactly. On my engine, however, the filler sounds a little different. I have a hinged snap shut rectangular "door", so there's no way to adjust how tight it seals. Seems like it's either going to be snug or loose, depending on the state of the seal. It's also not an o-ring, but rather, a closed-cell like foam that covers the whole inside of the cap. I'll see if that seal can be replaced...
John O	posted 09-04-2003 04:19 PM ET (US) Same leak problem on my Mercury 2001 75hp 2 stroke. This is a new motor. I found that I must fill just above the "ADD 1 QUART" level to minimize spilliage. I do see some drops from time to time but I think it is from the carbs.
newt	posted 09-04-2003 10:02 PM ET (US) Same problem on a 2003 Mercury 90 Classic (2-stroke) - since motor was new. I am too lazy to pursue a remedy.
whalernut	posted 09-05-2003 03:55 PM ET (US) I am not trying to be rude or anything, but is there a way you could convert them to 50/50 mix and mix the oil and gas in the tank? I really like the simplicity of that. I hope you all work out the leaky problem, and if you find out a solution, please post the remedy :-) Jack.
j_anicker	posted 09-05-2003 05:06 PM ET (US) It might be possible to convert the engine to non-injection and use pre-mix. Not sure... However, I did find a conversion kit for the oil tank from Mecury, about $199, that moves the tank off the engine to a pressurized tank that can tuck away in the lazerette. Link below: http://www.mercurypartsexpress.com/PartsExpress/ProductSelection/Accessories/getProductGroup.asp?CID=163160187068235063274&lvlOneKey=35&key=1400&level=3&store=Accessories Kind of a spendy fix to an obvious design flaw! I'm going to start with a new gasket and only keep the tank 1/2 full and see how it goes. Thanks for the help!
newt	posted 09-05-2003 10:03 PM ET (US) The leaking oil doesn't bother me enough to convert to pre-mix, and I find the on-engine oil tank is handy. Simple green takes the oil off easily enough also.