1994 Force by Mercury 120HP oil leak

[ggundersen3]

I noticed a drop or 2 of black oil on the garage floor under my Force 120 in between uses( a few days). I recently installed a transom saver so the motor stays in the "far up" position in between uses. It didn't do this before I installed it. It's a '94 2 cycle so there is no crankcase or oil injector or anything. Whats is that black oil? The lower unit gear oil fill and drain plugs all look tight and don't appear to be where its leaking from. It sort of looked like it may have come from that tiny hole in the leading edge of the lower unit which I believe is the speedometer pick up hole. Not sure though. Concerned about it because if oil is coming out, lake water is getting in. Thoughts, ideas?
Motor runs fine though.

 

[pnwboat]

Wipe the oil up on your finger and smell it. If it smells like gas, then it's probably 2-stoke oil residue from the exhaust. If it smells like sulfur or something similar, then it might be gear oil from the lower unit leaking out somewhere.

 

[ggundersen3]

Thanks for the advice. I did that and its mysterious. Its an oily black substance but really has no odor. After further examination it looks like it might have run out of the tiny drain hole on the right side of the lower unit right behind the water intakes. Is it possible its just lake water mixed with exhaust residue that being held in there because motor is tilted all the way up in between outings? Or is it something more than that. It's like black oil with no real odor. Looking for an explanation.....

 

[pnwboat]

My guess is that it's most likely just exhaust residue (2-stroke oil/water) if it's coming from the drain hole. Gear oil doesn't loose it's smell and it has a very distinctive odor to it.

 

[ggundersen3]

Thanks! So in other words, don't be over concerned?

 

[pnwboat]

No, I wouldn't be too concerned.

To remove any doubt, you can check the lower unit oil by removing the oil drain plug on the bottom of the lower unit to check for any signs of water.

Just be careful to not remove the lower unit shift lever pivot pin. It's located towards the bottom of the lower unit on the side. If you remove this pin, you will most likely have to remove the propeller shaft and propeller shaft bearing carrier unit to get it back in.

The drain plug is item #2 in the diagram below. The shift pivot pin is item #6 in the diagram below. Stay away from the pivot pin.

http://www.crowleymarine.com/mercury-outboard/parts/1470_250.cfm?mdl=8WPRNM

 

[ggundersen3]

Will do. Thanks.

 

[ggundersen3]

I did that(removed the drain plug) and the gear oil looks perfectly 100% clean like the day I pumped it in there a few months ago. So it's not a lower unit gear oil leak. So I'm safe to assume it's exhaust residue. Thanks for the advice!

 

[jerryjerry05]

Yup your safe.