Gooey muck from exhaust

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spitfire9au

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Jan 2, 2005
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After shutting down my outboard there's a black gooey oil that slowly seeps from the exhaust, dripping from the centre of the prop. My first thought was gearbox but I'm fairly certain it's not from there. I've replaced the gearbox seals and it still happens. Also the gbox oil is clean, no water and the level stays the same. Over a few days there's probably around 20 or 30 ml leakage. It smells of exhaust and not like gbox oil at all. <br />I'm thinking maybe a blockage in the exhaust causing unburnt oil to accumulate and then gradually seeping out. So far as I can tell the motor runs ok. I have twins and the other motor is clean as a whistle. They're 1984 70hp Evinrudes, premix at 50:1. <br />Anybody have any ideas where I should start checking? <br />Thanks, Jeff.
 
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b22smith

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Jan 19, 2004
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Re: Gooey muck from exhaust

I had the same question about a used 25 hp motor I just bought and everything I've read about it seems to confirm that it's just accumulated unburnt fuel. Did this happen while running at low idle speeds? Have you run the motor recently on the water at high speed to clean out the system? Mine was fine after I did that and sprayed some SeaFoam into the carb to clean out the system. I'm sure some of the more experienced guys on the site can add to this.
 
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spitfire9au

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Re: Gooey muck from exhaust

Pretty sure it is just accumulated unburnt fuel...I always flush it out after use on the muffs so it idles for about 15 minutes or so and I've never cleaned out the system with Seafoam. Seems strange that it's only one motor that does it though, they are both treated exactly the same.
 
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umblecumbuz

Lieutenant Junior Grade
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Sep 25, 2004
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Re: Gooey muck from exhaust

Agree with Jeff.<br /><br />Odds are heavily with unburnt fuel/oil mix, in which case normal and nowt to worry about - except stains on the concrete.
 
7

71whaler

Petty Officer 3rd Class
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Jul 14, 2004
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Re: Gooey muck from exhaust

I have the same issue with my 1983 75HP Evinrude. Everyone I have talked to has said this is perfectly normal and is unburnt fuel. If you are worried about stains on the concrete get one of those oil absorbent pads from the auto parts store.
 
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Frank I.

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Nov 13, 2004
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Re: Gooey muck from exhaust

Its normal but make sure your engine is at operating temp when at idle(140degrees)If your running cold that will produce a lot(more than normal)of unburnt fuel
 
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the machinist

Senior Chief Petty Officer
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May 7, 2002
Messages
711
Re: Gooey muck from exhaust

Yes, it could be very normal. BUT have you compared compression between the 2 motors. You could have worn compression rings also, which would contribute to about the same situation.
 
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walleyehed

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Re: Gooey muck from exhaust

Do you stick with one brand of oil, or have you changed for any reason????
 
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spitfire9au

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Jan 2, 2005
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Re: Gooey muck from exhaust

Sorry about the delay, been away on hols. Haven't done a compression check as yet, guage pooped itself. I'll do one as soon as I can. As for the oil, yes I did change brands but it does it with both brands.....Valvoline and genuine OMC stuff. Oh yeah, I'm pretty sure the temps are ok, both feel about the same and have new thermostats.
 
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Lkoschak

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Re: Gooey muck from exhaust

If you can keep you hand or finger on the the top of the cylinder head at idle the engine is too cold. 140 deg at idle is too hot for most finger for more than a second. It's got to be 140 deg. The goo is an emulsion of oil and water.
 
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ob

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Re: Gooey muck from exhaust

This may be sort of a quantum leap here ,but I'm wondering what the engine is propped to turn at wide open throttle.Lugging an engine over time will produce similar buildup.Those 3 cylinder loopers like to breathe easy and should rap to 6000 with a light load.<br /><br />Otherwise as mentioned above,an engine running too cold as a result of stuck open T/stat bypass or removed T/stat will result in buildup as well.<br /><br />I've run several 2 and 3 cylinder loopers over the years and have never had this problem.
 
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Qld_Kev

Petty Officer 3rd Class
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Dec 4, 2004
Messages
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Re: Gooey muck from exhaust

I would give the Seafoam/decarbon a go first, it will clean all the gunk out. The only other thing I'm thinking are the engines getting loaded evenly? If that engines cable is a bit tighter it will be labouring harder, whilst the other one is taking it easy. You would probably notice a differnce in fuel usage if they run on seperate tanks.
 
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spitfire9au

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Jan 2, 2005
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Re: Gooey muck from exhaust

Think as big308 suggests, I'll try the seafoam route next, can't hurt and probably a good idea regardless. Won't have a chance to do anything for a week or so as I'm away again...this time working though and the weather couldn't be better either.....frustration!!!!!
 
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spitfire9au

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Jan 2, 2005
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Re: Gooey muck from exhaust

Fixed!!! Removed the lower unit and the rubber exhaust seal didn't look at all healthy. Oil all over the water pump area do I cleaned it all up, replaced the seal and it seems to have done the trick. As luck would have it I had a spare one in the shed so all it cost was a couple of hours. So I guess the exhaust was leaking into that area, the unburnt oil was building up while it was running and then leaking back out again via the exhaust after it was shut down. Now all I need to do is find those elusive fish!!
 
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