Lower unit oil seal Johnson 15hp

[Bad Wolf]

Newbie question. First I’m happy to have found this forum, there seems to be a lot of good information and help here.
I just bought my first boat and motor (used), and I’m starting to make a list of things to do.
I picked up a 1985 Johnson 15hp electric start. Seems well taken care of and starts right up, though so far it’s just been in the tank. After laying it down I noticed that a small puddle of coffee colored oil formed under the prop/lower unit overnight. From my readings I infer that there is some water in the oil, and that there must be a seal leaking somewhere. I was going to replace the lower unit oil anyway. There looks to be two seals and an “O” ring on the prop shaft. Are these the likely culprits? How difficult are they to replace. The PO said he had recently replaced the impeller/water pump.

Thanks
Many more questions to come.

 

[chevyrulz]

After laying it down I noticed that a small puddle of coffee colored oil formed under the prop/lower unit overnight. From my readings I infer that there is some water in the oil, and that there must be a seal leaking somewhere.

"coffee" colored oil could just be used oil. milky whitish grey oil has water in it. are you sure it didn't come from the fill or drain plug o-rings?

There looks to be two seals and an “O” ring on the prop shaft. Are these the likely culprits?

yes, if the fill/drain o-rings aren't leaking. these fill/drain plugs tend to work themselves loose over time, i look for oil on the lower unit every time before i back the boat in the water & i check the torque on those 2 often

also replace the o-rings on the fill & drain plugs each season when you change lower unit oil

 

[cajuncook1]

Before you tear into anything. Smell, the mixture. It is very common to have drainage of unburned mixture of fuel/oil and water. It is a 2 stroke, this is common.

After you wipe everything up. Place your motor back on the stand or boat. Drain some of lower unit oil and inspect it and smell it as well. There should be 2 distinguished smells (lower unit oil) and (burned mix of fuel/oil/water).

Edit:
The lower unit oil (inside the gear case) should not be milky. If it is milky then there could have been some water intrusion into the gear case. We can review that when you report back with what you find.

Please what ever you do, stay away from the phillips head screw near the foot of the gear case. I supplied pictures of the upper and lower oil fill screws. There should be a plastic or fiber washer behind them to help seal the holes and prevent water intrusion.


To refill the gearcase, use any good marine grade gear oil that is 80wt to 90wt. Evinrude sells an excellent gear oil.

 

[Bad Wolf]

I should clarify: I take my coffee with cream, ergo the stuff leaking out is light brown in colour. There is nothing coming out of the drain plug rather it looks like its coming out from inside the prop and at the joint between the prop and the housing.

Cajuncook thanks for the warning on the Phillips head screw, I had already picked that up from LeeRoys Ramblings, but it bears repeating. Those are the kind of insights that I appreciate.

I'll replace the gear oil this weekend and see how much leaks out. Once I get it in the water I'll have a better idea of how bad the leak is.

 

[cajuncook1]

Newbie question. First I’m happy to have found this forum, there seems to be a lot of good information and help here.
I just bought my first boat and motor (used), and I’m starting to make a list of things to do.
I picked up a 1985 Johnson 15hp electric start. Seems well taken care of and starts right up, though so far it’s just been in the tank. After laying it down I noticed that a small puddle of coffee colored oil formed under the prop/lower unit overnight. From my readings I infer that there is some water in the oil, and that there must be a seal leaking somewhere. I was going to replace the lower unit oil anyway. There looks to be two seals and an “O” ring on the prop shaft. Are these the likely culprits? How difficult are they to replace. The PO said he had recently replaced the impeller/water pump.

It is perfectly normal for black to light brownish stuff to ooz out near the prop. It is a through hub exhaust system. The exhaust and mixture of unburnt fuel/oil/water build up in the exhaust housing. When you lay it down after running in the barrel or on muffs, it will collect and drain out just as you describe. A lot of times the stuff drains out on the way home from the lake, so we may not see any of it when we get home. :wink: :wink:

The reason I told you to check your lower unit oil was to see if it has water intrusion or contamination inside the gearcase. If you have a leak, it will definitely be apparent. If there is a leak, then there could be many causes.

I think that the puddle of goo you saw was a mixture of unburnt fuel, oil and water. (I have a 1984 Evinrude 15hp motor on my boat). Seen the puddle before. But, please do diligence, I certainly would want to rule out a gear case leak!!!

Some causes of water intrusion and leakage/;

- leaking/worn/broken/missing/2 doubled up fiber or plastic o rings from the upper and lower oil drain screws.
- leaking shift shaft seal
- leaking drive shaft seal
- leaking prop shaft seal
- fine crack or fissure in lower gear case.