Inline six mercury lower unit

[1978allison]

When I run my 1977 inline 115 mercury outboard I am getting a gray mixture by the locking ring on the lower unit that run out on the pavement after it sits for a while.Have done pressure test, held 15lbs for 20 minutes. Any suggestions.

[Glastron1987]

I'm guessing but gray means aluminum to me. Is the prop rubbing on the lower unit for some reason?

[1978allison]

It is a gray mixture with water and something coming out by the lock ring in the gear case and going down the skeg.
If you were running the engine on a engine stand then you would see black unburnt fuel and water coming out this area when you turned the engine off.

[W2F a V-King]

Sounds like water mixing with the LU oil. If you over filled it, it could be expanding when warm and pushing out the prop shaft seals.

Water can get into the case from several places. Might have held a pressure test, but regardless. Drain the fluid and have a look. If it's contaminated it's time to reseal it.

[Gmcviper]

I would say exhaust chest gaskets if you can't pin point the gearbox. I had a i6 that was having grey sludge in the prop. the block was cracked leaking water in the port area, the same thing happens if the gaskets are bad. If this is the case it will cause mechanical failure.