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A couple of weeks ago I did the early season preventative maintenance on my Yamaha F50. I changed the engine oil, the spark plugs, and the lower gear lube.

A couple days later I noticed a small puddle of oil under the lower unit. It seems to be leaking out of the lower plug. I've unscrewed the plug and put it back in. I've replaced the paper washer and put the plug back in. I thought the original paper washer may have been stuck in the depression where the plug goes and dug around in there but it didn't appear that there was one, and it still leaks! I probably had a teaspoon or more under the lower unit this morning.

Anyone got any ideas on what my problem is? Should I go buy a new lower plug and try that?

Boating season is here, and I'm not out on the water!!!!!!!

Thanks for any help you can provide.

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My 70hp Yamaha 2-stroke had a small red rubber washer, not paper. I had to replace after many years as it was torn. Only other thought is that the plug got cross threaded and stripped the lower end. Plug is stainless and housing is aluminum. I have not heard of that happening though.

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I second Mtown's comment. O-ring.

I changed the O-ring each year as a precaution.

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Should I go to the Yamaha dealer for an O-ring, or just take the plug to an autoparts store? How tight on the plug should the O-ring be?

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Could also be a shaft seal. Not too familiar with yiur engine though. Since you say iys from the plug, change the washet seal everytime you open the drain screw

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I would use only an OEM O-ring. Proper diameter is important but thickness matters about as much. You don't want the plug to stand proud of the gearcase when torqued properly.

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OEM is a paper washer, not an o-ring.

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I am surprised. My 2003 Yamaha F115 was rubber.

In looking up the parts on Simyamaha.com for a post 2006 F50, I see what appears to be a paper washer. I would look at your model/serial number and look it up.

www.simyamaha.com

If it is paper, I would try a new washer and tighten it down with a screwdriver till it is snug, then a bit more but not really hard.

Do you have a service manual? If not, I would get one. The Yamaha Service manuals are very good and worth the $.

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On my 2001 60 the seal is a light blue plastic washer, I got a pack of OEM and replaced them.

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Mine's a 2008 and it's paper.

Just for sh*ts and giggles, yesterday afternoon I put the plug in without the doofy paper washer, and it oddly enough leaks less, but still leaks.

I might get a new plug and see what happens.

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The drain plug seal is called a "gasket" for Yamaha's. The current part number is 90430-08020-00

http://www.boats.net/parts/detail/yam...20-00.html

...and appears to be used on yamaha models going all the way back to 1984 when they were first sold in the US under their own name.

"Gasket" implied a flat washer not an O-ring, but manufacturers change parts all the time. OMC/BRP has gone between spastic washers and a rubber O-ring and back. Mercury has used plastic washers and fiber washers, both are available.

I would take a very careful n close examination of the both the drain plug and the gearcase where it seats looking for a burr that is tearing up the gasket or otherwise foiling the seal.