Lower Unit Leaking Lube Oil

[WrenchHead]

I'm running a 2004 Merc 60 hp 4-stroke EFI and recently I replaced the two seals for the prop shaft and also replaced the O ring separating the lube oil sump from the exhaust chamber. I used compressed air at 10# in the lube oil sump and sprayed soapy water on the O ring and the seals to check for leaks. The air pressure held at 10# and I didn't see any soapy bubbles. So I vented the compressed air, filled the lower unit with lube oil, and left the prop off so I could check for an oil leak from the O ring into the exhaust cavity. After three days I see oil began to puddle in the exhaust cavity. How can the unit pass the compressed air test but then have lube oil seep past the O ring into the exhaust cavity?

 

[MH Hawker]

what color is the leak, it may be 2 stroke

 

[WrenchHead]

what color is the leak, it may be 2 stroke

No maybe to it -- it's four stroke. The leak is the same color as the lube oil I pumped into the lower unit. I have not run the engine since I installed the seals and O ring.

 

[MH Hawker]

sounds like a do over, this is the more or less standard for testing a LU, 15 lbs pressure, then 5-6 inches vacuum for at least 20 minutes. Use soapy water to find leak's if it doesn't hold pressure.

 

[WrenchHead]

Yeah, I know it's leaking so I'll disassemble, inspect, and reassemble with new O ring. Then test as you suggest.

 

[GA_Boater]

Spin the driveshaft, prop shaft and shift shaft while under pressure or vacuum. The LU may hold static pressure/vacuum and leak when the shafts are turned.

 

[WrenchHead]

Spin the driveshaft, prop shaft and shift shaft while under pressure or vacuum. The LU may hold static pressure/vacuum and leak when the shafts are turned.

Thanks.

 

[MH Hawker]

i test mine ever fall when i bring it home for the winter, that way if it fails i have 2 mouths to get it fixed