Johnson 15 HP (1988) Producing an oily goo when run in test tank. Is this an issue?

The Famous Grouse

Petty Officer 1st Class
Joined
Sep 26, 2008
Messages
291
Hi everybody,

Thanks to previous advice I did a total carb teardown and thouough cleaning on my 1988 15 HP Johnson. It now runs much better and it will allow me to throttle down without dying. I found a mass of some kind of fibers like wool wrapped around the throttle plate, so I assume there was probably other grit/junk in the carb as well.

In the process of verifying that the carb fix worked, I ran the outboard in my "test tank" for about 10-15 minutes. My test tank is a plastic garbage can and I'd estimate it has 15 gallons of water in it.

Now I've got an new situation that I'm worried about: When I got done running the engine in the test tanks, I noticed there was an oily, frothy gray goo on the surface of the water.

When I poured the water out of the tank, this gray slime was clinging to the sides of the tank and there was also a slick of it built up inside the prop hub. It's like a very thin wet grease.

Then last night I noticed that this wet goo has continuted to drain out of the engine and a small pool of about 1/2 cup of it was on the floor beneath the engine. It looks like this little pool drained out of the exhaust hub.

What is this gunk? Is this normal for a 15 minute test run or do I have some kind of major issue here?

Maybe this is normal because the engine is recycling the water, so in my mind this could be just combustion by product. But with that said, it seems to me to much more than I'd expect, but I've never done that much tank-testing of a running outboard before. Mainly when I test an outboard, I run it on the garden hose for a few minutes.

Is this normal?

Many thanks.

Grouse
 

Watermann

Starmada Splash of the Year 2014
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Jan 12, 2013
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13,747
Re: Johnson 15 HP (1988) Producing an oily goo when run in test tank. Is this an iss

Hey Grouse,

I have only seen gray goo when oil and water mix. Anything to do with combustion is black. I would say drain and check your lower unit gear oil to see if it matches your mysterious gray goo.
 

kfa4303

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Sep 17, 2010
Messages
6,094
Re: Johnson 15 HP (1988) Producing an oily goo when run in test tank. Is this an iss

Hi grouse. The oily goo is perfectly normal when running a 2-stroke in a test tank because it is recycling a small amount of water over and over. Any excess water/exhaust mix can/will continue to drip out after you have removed the motor from the water as well. Check out youtube for vids of motors running in test tanks and you'll see lots of smoke and water that looks like dirty chocolate milk. Not to worry, it will run much cleaner on the ope water. Unless you leave a noticeable oil slick behind you while underway, you'll be fine.
 

The Famous Grouse

Petty Officer 1st Class
Joined
Sep 26, 2008
Messages
291
Re: Johnson 15 HP (1988) Producing an oily goo when run in test tank. Is this an iss

OK, thanks for the feedback.

I thought about it being lower unit seals, but two things ran aginst that. Frist, this motor has been hanging in my garage all winter, so if the seals were leaking, there'd be oil underneath it. Second is that it has not continued to leak the dark, heavy lower unit oil. What's leaking is the geasy, gray goo that I described.

To KFA: Dirty chocolate milk is a perfect description.

I thought I might have a dead cylinder, but there's no raw gasoline smell, or anything like that. Both cylinders have spark as well, so then I was out of ideas.

OK, so its sounding like this is "normal" and just a case of recycling the water too many times and buidling up conbustion residue in the test tank?

Grouse
 

Putzaroni1

Petty Officer 2nd Class
Joined
Oct 20, 2012
Messages
108
Re: Johnson 15 HP (1988) Producing an oily goo when run in test tank. Is this an iss

Hey Grouse,
Just found your post because I have the same issue with an 84 Evinrude 15hp.
After running the motor if I lay it on it's back it has grayish brown stuff draining out between the prop and the lower unit.
I just pulled the prop off, cleaned out all the goo, replaced the water in my test tank (garbage can) and ran it again. It is doing the same thing. I guess a trip to the lake to see if it does it there after a good run is my next step.
It makes a mess and I'd like to get to the bottom of where it's leaking. I'm guessing the only way is to do a pressure test but I'll report back after a good run on the lake. Please do the same if you have any further info.
 

82rude

Rear Admiral
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May 8, 2012
Messages
4,082
Re: Johnson 15 HP (1988) Producing an oily goo when run in test tank. Is this an iss

you can take it to the lake and run it all you want but as soon as you put it in a barrel you will have the same result.its the nature of the beast.if you want to put your mind at rest check lower unit ,no water in oil no issue but even if you had a totally perfect lower unit you will still get the gunk in a barrel no matter what.
 

tomhath

Master Chief Petty Officer
Joined
Dec 5, 2007
Messages
814
Re: Johnson 15 HP (1988) Producing an oily goo when run in test tank. Is this an iss

Yup. A two-stroke, especially when it's cold, doesn't burn all the oil in the fuel. No place else for it to go except out the exhaust.
 
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