Mercury 4 stroke 8 HP lower unit oil leak

[ecurnutte]

I recently purchased a 2006 mercury 8 hp four stroke serial number OR108706.

Before purchasing we backed it in at the ramp and checked things out. I checked forward, reverse, idle, etc. Everything seemed great.


After running it in the water for several minutes I drained the lower unit oil to make sure there was no water in it. I was fortunate enough to be next to a small marina where a marine mechanic looked at it with me and said the lower unit oil looked great with no signs of water.


Today I took it to the car wash and after returning home I trimmed the motor up (it's manual) and then saw some oil leaking out of the small hole directly left of the lower unit fill/drain screw. This is more black in color and not the more green lower unit oil color. Is this a significant problem? I have a trip planned soon, would it be a problem to use this several hours? Any guidance or direction would be appreciated. Thank you.

[ecurnutte]

Update:

I also decided to check the 10w-30 oil level. Pulled the dipstick and oil just started pouring out like crazy. There was roughly 1.5-2 times the recommended 800ml in there. Thanks again for any help that you could provide.

[SilverFox579]

Update:

I also decided to check the 10w-30 oil level. Pulled the dipstick and oil just started pouring out like crazy. There was roughly 1.5-2 times the recommended 800ml in there. Thanks again for any help that you could provide.

If engine was vertical when you checked oil, crankcase is/was overfilled. Oil should not pour out of the dipstick hole. I would NOT run that engine again until the oil level is adjusted to proper level. Would be to your advantage to acquire an owner's manual for your engine and any Mercury dealer can get one for you.

[ecurnutte]

Thank you. The motor was completely vertical. Before I put the dipstick back in, a large amount of oil made it on the ground. Then I drained it per the manuals instructions. I measured out 800 ml and still had plenty in the disposal container left. Considering what was left in the container and on the ground, it was at least 1.5-2 times full. Should I be safe to run this after putting the correct amount of oil in? I will also note that it seemed to run perfectly when backing in and testing it when I purchased (and was obviously overfilled). Thanks again.

[ecurnutte]

Update: I put the correct amount of engine oil in, cleaned spark plugs, and ran it on idle for 5 minutes. Then ran in forward and reverse and all seemed fine. The oil now appears to be coming from between where my prop and lower unit meet. It is a grayish, foamy, milky substance. Again, after running it a bit and draining lower unit oil, there are no signs of water I can see. The lower unit oil looked good and even with an empty lower unit, there is still some of the milky stuff collecting around the prop. Thanks again for any guidance you can provide.

[SilverFox579]

I'm assuming you have properly re-filled lower unit.

The milky stuff you're seeing is probably oil that ran down from top. I'd keep a close eye on engine oil level, should be at middle of range on dipstick, and run the engine. Spray some "green" or "orange" degreaser to remove what you're seeing on the lower unit. Do this after every run so you start with a clean lower. I'd bet the milky stuff will stop after a few outings.

[ecurnutte]

Thank you sir. All levels have been properly filled and I am no longer noticing.

[billnorman1]

If you removed the engine oil and replaced only the specified amount, I personally would be hesitant to put that oil back in. Either it was overfilled or "made oil" from gasoline washing past the rings. If it was diluted with gasoline it is not a good lubricant. If it was overfilled you still do not know the quality of the oil used, it might not be marine quality 4 stroke oil with rust preventive.
Bottom line- it's your motor. I never put any liquids in mine that I did not purchase, I even check my non-ethanol gasoline occasionally.