Oil and water

irishfan · Apr 17, 2010

I ran my 6hp merc in a barrel today. After running it I noticed a brown oil coming from the middle of the prop. It does exhaust thru the prop. Is this just residue from the exhaust or is the gear lube leaking somewhere and it is running out the prop?

njj502 · Apr 23, 2010

I'd say it's fine. Prob just oil/gas/water mix exiting the prop.

Nick

MeanMouth · Apr 23, 2010

I don't want to alarm you, but it just might be gear oil coming through, especially if it's thick.

After draining the lower unit oil on my '76 15hp Johnson, I pulled the prop off. There is a seal that keeps the gear oil from entering the exhaust, which sort of sounds like the issue you've noticed.

It's a VERY simple job, so I suggest you drain the lower unit, pull the prop off, and check the seal. It was a $0.95 gasket at my local marine store, along with $10 for the gear oil. Even if it's not the seal, at least you've maintenanced the lower unit for the year.

Just a suggestion to make sure you don't lose the lower unit...

bassboy1 · Apr 24, 2010

99% it is unburned fuel/two stroke oil. 2 strokes don't burn as efficiently at idle, thus you are always going to have some unburned crud coming out after idling a while.

1% it is gear lube. If you want to check, just drain and refill your gear lube. If the lube comes out clean, you're good to go. If it comes out milky, you have a leak. If lube is leaving, water will be taking its place, so you will notice the milkiness when draining.

MeanMouth · Apr 24, 2010

bassboy1 said:
99% it is unburned fuel/two stroke oil. 2 strokes don't burn as efficiently at idle, thus you are always going to have some unburned crud coming out after idling a while.

1% it is gear lube. If you want to check, just drain and refill your gear lube. If the lube comes out clean, you're good to go. If it comes out milky, you have a leak. If lube is leaving, water will be taking its place, so you will notice the milkiness when draining.

1%? Unburned fuel will most likely be stuck to the housing and would appear black; somewhat like dirt, and resembles a dated spark plug.

A picture might help the situation, but no one knows what's coming out of the exhaust because we're not looking at your motor.

The only way to tell is to check yourself. Brown oil sounds like it is contaminated. We're talking the color of the oil, not particles of unburnt fuel.

njj502 · Apr 25, 2010

Oil + fuel + the cooling water the midsection sees makes brown sludge. Don't ask how but it does. Pull the plug on the lower. If it's not milky don't worry about it. That sludge will clean itslef up.