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2006 Mercury 15jp 2 stroke air bubbles coming from carburetor

K

kls

New member
My 15 hp Mercury 2 stroke is having issues.

The engine starts fine and idles fine
It runs WOT fine as well

The problem is air is bubbling up from the fuel inlet on the carburetor.
It also shakes frequently when going slow from the boat to the dock.

I have rebuilt the carburetor with new pump diaphragm and gaskets a coupttimes. It did start to run better after doing this, but the air and shaking problem still exists. I believe the shaking is caused by the air being generated inside the carburetor band mixing with the fuel causing the engine to shake. The air then bubbles up from the fuel inlet and fills the fuel line with air. There is no gad leaking out anywhere.

Any idea where this air is coming from?
 
Is it air you are seeing ?---Could it be fuel vapor ?-----Have you adjusted low speed mixture needle to see if it smooths out ?
 
racerone said:
Is it air you are seeing ?---Could it be fuel vapor ?-----Have you adjusted low speed mixture needle to see if it smooths out ?
Click to expand...

I am not positive what the contents of the air bubbles contains. It very well xould be fuel vapor. I will adjust the screw and report back.
 
kls said:
I am not positive what the contents of the air bubbles contains. It very well xould be fuel vapor. I will adjust the screw and report back.
Click to expand...

I tried the idle screw, no change. But I also hooked up 1 hose to the fuel tank to the inlet and the air stopped. I guess it is an air leak in the lines.

Thanks for your help
 
Why is your fuel line not running through the fuel filter? What screw are you adjusting? the one on the front of the carb or the one on the throttle cam? Did you soak the carb and give it a good cleaning when you rebuilt it? Adjusting the screw on the front of the carb should have had an effect.
 
flyingscott said:
Why is your fuel line not running through the fuel filter? What screw are you adjusting? the one on the front of the carb or the one on the throttle cam? Did you soak the carb and give it a good cleaning when you rebuilt it? Adjusting the screw on the front of the carb should have had an effect.
Click to expand...

The reason for the fuel line not running through the filter is 2 fold.
1. I am getting rid of the connections inside the engine as a process of elimination to find the bubbles.
2. There is another filter/water separator upstream.

The screw on the front. The one that you turn 1 3/8 turns out as a place to start tuning the air fuel mixture.

I have cleaned the carburetor 4 times using an entire can of carburetor cleaner each time. It does idle very well and runs good at WOT
No, I did not soak it.

The screw had the effect of making the engine run better or worse as one turns it, but the bubbles coming from inside remain.

Could this be caused by a leaking oil seal?
Or by a bad/failing coil?

Compression on each cylinder is 110.
 
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