Lower unit oil leak

[Granny]

I noticed a puddle of lower unit oil that had leaked out of the prop and prop area. Would this be a bad seal? If it is how hard is it to replace? Its an 1988 120hp Johnson.

Thanks in advance,

Granny

[New Yankee]

Granny,

Could be a bad seal - last year I posted to see how hard it would be to replace mine (50 Merc) when I had the same issue. I pulled the prop and took a birds net of line off the shaft, replaced the prop and contemplated the seal job. Much to my supprise (this NEVER happens to me ) it never leaked again!

May be worth a try before you break it down.

[norm]

first off, are you sure it's gear oil thats leaking and not just the black gunk from the exhoust housing? gear oil should not be too dark and will have that distinct smell to it. Exhaust gunk is really dark black and will not smell like gear oil. I have seen a few times where the exhaust gunk is coming out and people think their lower unit is leaking.

If you are certain it's gear oil coming from that area its a bad prop shaft seal or bearing carrier o-ring. it involves taking off the propeller, pulling out the bearing carrier, puling out the old seal and pressing in a new one. It's not too tough of a job but you will probably need some special tools to pull the bearing carrier and to pull out the old seal/put new one in. I personally would bring it somewhere and have them reseal the whole gearcase. Hope this helps!

[Surface Tension]

If its black its just residue from the exhaust and nothing to worry about. If its clean oil then you have a leak in your lower unit somewhere and its most likely the seal on the prop shaft. If its been sitting in the same spot it spent the winter the shaft and seal would have contracted from the cold and oil leaked out. It may be fine with the warmer temps now but its and indication the seal isn't 100%. You can get a seal kit and it'll include all the seals in you lower unit along with purchasing a manual to guide you through the process or pull the lower unit out and have a shop do the work for you. While your at it have the impeller replaced. Parts would be under $100 and your looking at about an hour labor.

[musky hunter]

There could be several causes of the leak. Of course, merely replacing the seals is step #1. It can be tedious removing the old seals, I would recommend getting a manual for your motor before embarking on the task. But it could also be due to a problem on the shaft inself. "Fretting" is a condition caused by chemical corrosion in the direct area under the seal itself, and would be characterized by an annual groove. Or the shaft could be bent. You won't know until you remove the seals and inspect the shaft. Hopefully, all it requires are seals.

[Granny]

Thanks for the info. I picked up the seals and I am going to pick up a manual this afternoon before I start in on it. I will give that a try and see if it does the trick.

later,

Granny

[8-Ball]

I too just got boat from storage, and there was a small area of black something below the prop-about the size of a silver dollar. Also, about 1-2oz. of water came out when I lowered the engine down. I drained the lower unit last fall and put in new oil-did not have a funny color, or water, or any little metal shavings in the old oil, so I thought all was good. Should I be concerned ? If so, what are your thoughts? 8-Ball.

[out_fisherman]

I think there are lots of sets of lower unit seals

being sold for nothing.

[Surface Tension]

8ball thats just crud from the exhaust getting washed out by gas dripping from the carb when you tilt it.

[8-Ball]

Thanks ST- I will keep an eye on it and make sure it does not happen on a regular basis...