Oil Leak in Nissan

It's a NS9.9C short shaft, 2 stroke. I noticed on my last sail last season that oil was leaking out of the vertical seal about 3/4 of an inch in front of the prop on boat sides of the motor. I covered her for the winter and when I uncovered it, I noticed oil dripping from the prop end itself. I'll try to add pics here:
http://www.flickr.com/photos/26593864@N07/4637918380/
http://www.flickr.com/photos/26593864@N07/4637309789/
http://www.flickr.com/photos/26593864@N07/4637310573/





Can I replace the gasket with a generic type and cut it to fit, or do I have to buy a Nissan replacement? Or is the problem more serious?

Thanks... Steve

The material on the prop shaft looks like unburned fuel (oil/gas) residue. Have you changed the LU lube lately? If you need them, you can get seals from any Tohatsu/Nissan dealer.

If the LU lube means, did I change the oil lately... well I change it at the start if every season. I believe I may have caused the the problem by over filling the oil last year. The liter bottle I bought the year earlier was low and I couldn't quite fill it from the bottom as the manual states, so I topped it up from the top screw, so it was very full.

If LU means something different, please explain. The substance feels and smells like oil.

again... Thanks... Steve

LU is industry shorthand for "Lower Unit".

Seals for the LU are available at any Tohatsu/Nissan dealer. Likewise, a Factory service manual is available. The service manual will explain the correct filling technique and proper level. BTW, the prop housing seal is an O-ring, and you need one that is precisely the right size.

Always fill to the correct level. If too low, you risk the driveshaft bearing failing. If overfilled (not sure how you could reasonably do that without tipping the motor on its side and "worrying in" extra gear lube), excess pressure in the LU could cause some lube to leak past a seal -- but may not damage the seal -- once the level is back to the correct level, it may not weep any more.

Change the LU lube. If it comes out clean, you do not have water contamination. If the drain material looks milky, it is contaminated with water, and the problem should be investigated promptly. At the age of a 9.9c, it's likely that it's time to do a re-seal of the LU. Also a great time to get a water pump kit installed. If these tasks are within your skills, great. If they seem daunting, it's prudent to get to a dealer for service.

Thanks for the reply. Learn something every day. I have a service manual, and I will buy the O-ring. The oil always comes out clean.

Steve

Just to let you know the results. A mechanic friend recommended that I drain the oil, tighten all the bolts, refill the oil properly, then check the results. I did that, and whawla... No more leaks. And she runs like the top I knew. Thanks for your help.

Steve