Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

[aridhol]

Evening, after my last trip out fishing I notice there was a puddle of oil below my motor and I'm wondering what it's from.
A basic google search indicates maybe the prop seal and it's gear oil leaking out? It's black as you can see in the picture, is gear oil black?

2 stroke, using 40-1 mix
Changed the prop probably 10 trips ago but this just started happening
No running problems, it goes along great.

Looking to the experts here for some advice on what it could be and any links/tutorials on fixing it. I don't have the service manual unfortunately.

 

[coolbri70]

Re: Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

gear oil should not be black, more honey colored. could be 2 stroke from the exhaust. if it is gear oil it needs changed, also 50 to 1 is the correct mix and 40 to 1 is rich and could explain the build up in the exhaust

 

[aridhol]

Re: Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

gear oil should not be black, more honey colored. could be 2 stroke from the exhaust. if it is gear oil it needs changed, also 50 to 1 is the correct mix and 40 to 1 is rich and could explain the build up in the exhaust

Thanks, I'll adjust the mix.

Would the oil normally leak behind the prop like that? I had a smaller 2 stroke and it'd always run out the prop itself (hole in the middle where the exhaust comes out).
I 'll adjust the mix and see what happens, I just wanted to be careful, don't know much about outboards.

 

[emdsapmgr]

Re: Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

Agree, what you are seeing is normal. It will leakout at the base of the prop.

 

[boobie]

Re: Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

It's normal.

 

[jwjw7108]

Re: Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

Yup, normal. I was concerned at first too. After taking to a few shops they all said the same thing. Just. 2 stroke burnoff. Mines worse though. I run a 82 115johnson. Another thing said is that it was more common if you run it at trolling speeds for a long period of time.

 

[Gkm70526]

Re: Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

I had this same problem with my mariner 40hp come to find out I had my fuel/oil mixture to rich about the same as you have yours. I adjusted my mixture and I haven't had this problem again.

 

[emdsapmgr]

Re: Leaking black oil behind the prop - 1982 johnson 90HP - J90TLCNB

Engines that are running cold tend to have poor combustion. (thermostats stuck open) Poor combustion causes more unburned fuel to drain down the midsection and out the prop. You might want to confirm that both heads are running at least 145 degrees at idle.