Oily exhaust water

Papazoo

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Jan 5, 2022
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I have a 97 25 hp mercury 2 stroke that I notice a lots of oil in the water as I ran with muffs on. Also a lot of smoke. The mixture screw has to to adjusted almost completely in to lean for it to run . And even then it have a rough idle . Compression is about 105 each cylinder.
 

Sea Rider

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Welcome to IBoats,

What's the current fuel/oil mixture ratio, is it 50:1 or tad higher, which 2 stroke oil brand is being mixed with fuel ? It's normal for a 2 stroke motor to smoke a bit while being run on muffs, all does.. Check with a Service Manual how many turns in-out needs to be adjusted to for a smooth idling...

Happy Boating
 

Papazoo

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Thanks for responding, yes fuel is mixed 50-1. Quicksilver 2 stroke, not synthetic blend. Smoking very heavy, only runs with mixture screw turned almost closed.
 

Chris1956

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When was the last time the carbs were overhauled? Maybe the carb is flooding?
 

Chris1956

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Also, check the fuel; pump. If the diaphragm develops a hole, raw fuel is allowed into the crankcase, and can cause the symptoms you see.
 

Papazoo

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Also, check the fuel; pump. If the diaphragm develops a hole, raw fuel is allowed into the crankcase, and can cause the symptoms you see.
It’s been awhile since carb rebuilt , and what you are saying makes a lot of sense, thanks
 

hardwater fisherman

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It’s been awhile since carb rebuilt , and what you are saying makes a lot of sense, thanks
If you have this style carb the primer has a spring and a check ball.. The check ball can get lodged into the spring allowing fuel to pass through the primer. This happened on my 25hp and my nephews 15hp.
 

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Papazoo

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that’s identical to mine except I have the electric choke, thanks
From the responds I’ve received it looks like a carburetor rebuild will solve the issue. Thanks
 

Sea Rider

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After checking the carb and fuel pump condition as suggested, rebuilding the carb, changing the fuel pump's internal diaphragm or whatever needs to be done that 24 year oldie needs a long decarbon process thru the carb spraying at least half to 3/4 can contents of CRC marine engine tune up decarbonizer. More effective than Sea Foam which needs to be mixed with fuel whereas the CRC is directly sprayed pure.
CRC Decarbonizer.jpg
This product will soften and clean carbon build ups collected over the years in the exhaust, combustion chambers, rings and exhaust pipe. Once the long decarbon process ends run the combo hard on water for some minutes for the product to clear itself at speed. The motor will idle much smoother and smoke less than now.

Happy Boating
 

QBhoy

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Absolutely normal to see oil residue exit the exhaust. Simply because as an absolute principle of operation…a 2 stroke is what’s know as a total loss lubrication system. There will always be a sign of oil out the exhaust. Especially noticeable when running in your driveway on a trailer. Wouldn’t worry about it. I’d worry more, if there was no sign of it.
 

Papazoo

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Yes, I have notice some oil in the past but not like this and it is running very rough. I really think that what others suggested that the damaged diaphragm is causing this issue. Will post what I find as soon as I get a chance to look at it . Thanks for all the responses.
 

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QBhoy

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Yes, I have notice some oil in the past but not like this and it is running very rough. I really think that what others suggested that the damaged diaphragm is causing this issue. Will post what I find as soon as I get a chance to look at it . Thanks for all the responses.
Oh. Yeah. That’s a fair old bit of oil right enough. But could also be from oil sitting in the exhaust for a long time, perhaps. That looks more like the signs of age old oil build up sitting in the exhaust that’s came dislodged.
 

Papazoo

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I guess I need to run some if That Crc engine tune up that that Sea Rider suggested, sure couldn’t hurt. It may be I have a number of issues going on. Thanks for the input.
 

QBhoy

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I guess I need to run some if That Crc engine tune up that that Sea Rider suggested, sure couldn’t hurt. It may be I have a number of issues going on. Thanks for the input.
No probs. I’d be quite sure that is certainly partly burnt/unburnt oil…but equally as certain, not fresh unburnt oil of any time recent. Fresh oil that might flow through unburnt as a result of anything abnormal running conditions like carb set up or similar…would just come through looking not far off what it looks like beforehand. Black oil like this from a 2 stroke is usually from a build up over a length of time and sitting somewhere over time.
 

Papazoo

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Yeah , haven’t really thought about that does make sense, because I know the oil I put mix In doesn’t look like that,
 

QBhoy

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Yeah , haven’t really thought about that does make sense, because I know the oil I put mix In doesn’t look like that,
Don’t get me wrong..could be a sign of historical poor running issues or too much oil mix…but it definitely isn’t anything recent
 

Sea Rider

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There will always be a sign of oil out the exhaust. Especially noticeable when running in your driveway on a trailer. I’d worry more, if there was no sign of it.
For that escenario to happen the user simply forgot to add 2 stroke oil to his tank and the motor is running with pure fuel while being unattended at the driveway. A fully warmed up healthy motor smokes less than a cold one, but smokes anyhow...

Happy Boating
 
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Sea Rider

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There was oil mixed in the fuel at 50-1 , 100% sure of that.
Is that a second hand motor, you bought it new right out of the box ? imagine all the carbon filth collected over 24 years of operation at different throttle speeds. No matter which 2 strokes oil is being used at 50:1 ratio will always smoke. 2 stroke motors are smokers by nature and there's nothing you can do about them. CRC the way to go....

Happy Boating
 

Papazoo

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Update on the issues I was having with my 25 hp 2 stroke, I found a had a bad spark plug which I replace both, also remove carb and clean blowing out the jets with air compressor. Was able to adjust the fuel air mixture where before it would only run very lean. I did used the crc and ran it through my outboard according to can instructions. Motor now runs great, better than it has in a long time. I appreciate all those who advise me with this issue.
 
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