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1981 OMC 35 leaking green oil on midsection

T

tunahelper

New member
As the title says, I have a 1981 35 hp OMC that leaks green oil on the midsection. The motor runs great and recently has had a complete new gaskets and seals installed. The oil stain does not appear to have gas in it. The oil is not black either. I replaced the hose from the bottom bearing to the top bearing also.

What am I missing?

I would think the crankcase is in a vacuum.

Where could the oil be coming from ???
 
The 2 crankcases on your motor are pressurized when the piston is going down in the cylinder.-When the piston is going up it pulls new fuel and air into the crankcases.--------Do you run fuel out of the carburetor when done boating ?---Do you tilt the motor when trailering and when do you see this leak ?--Do you close the vent on your tank when done boating?---------Provide all the details you can.
 
I don't drain fuel from the bowl after running. I don't tilt the motor up after running. Normally I see the oil drips after running normally, not from sitting. Usually I only close the tank vent if a heavy rain is expected.

Do you think the leak is coming from the crankcase halves. The leak seems to only be oily, there is no gas smell so I think I can rule the carb out.

The motor runs so well that I assumed there can be no case leaks, but I may be wrong.
 
The leaking is dripping down from the rear of where the midsection attaches to the lower cowl. Sorry about the lack of proper terminology. All fuel lines have been replaced. The only place I think the drip is coming from now can be the crankcase joint as you pointed out. I think I used the wrong permatex sealer on it, there is no gasket for the crank halves. Sorry no pics.

Is there an auto part store sealant for the crank case halves. Will permatex black work?
 
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The crankcase joint is a " precision joint " ---which means you must be meticulous in your work. No burrs or imperfections allowed that might interfere with the surfaces coming together the way they were at the factory. It is important that bearings are located on the dowel and space for the upper bearing so that proper clamp up is obtained.---------The wrong sealer that does not squeeze out properly will result in trouble.------------Use OMC / BRP gel seal or Loctite 518.
 
Well, I started to pull the powerhead off this morning and made a interesting discovery. I pulled the flywheel off and noticed the top seal just sitting on top of the crankshaft. It had worked it's way out. The stator was very oily with the same green oil that has been dripping down the midsection. I think the mistake I made when installing the seal was tapping it even with the boss. The service manual shows it bottomed out into the boss.

Hopefully this will cure my oil dripping issues.
 
If you have used anything but Gel Seal II between the crank cases, keep on and re-do or you will soon be back in a mess again!!
 
I checked the sealant I used for the crankcase halves and it was Permatex anaerobic sealer. When I went to NAPA to get Loctite 518, the parts person cross referenced the Permatex product. Upon closer inspection of the crankcase joint, it appears to be sound.
 
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