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Belching and Smoking Mercury OB

J

John M.

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" I have a 83 model Mercury 15

" I have a 83 model Mercury 150, no oil injection. The outboard runs great at full throttle. The problem that I have is when it idles for a few minutes, it starts missing and smoking. I changed the plugs and this helps for a short time. After a full throttle run, it idles smoothly for a few minutes and starts missing again. Any of you Outboard "GURUS" have any ideas? Compression is 100 - 105 on all cylinders. "
 
Live on the Gulf Coast. Trie

Live on the Gulf Coast. Tried it with and without the thermostats. Same problem. I am at a loss. Any other ideas?
 
"John,

Do you notice any di

"John,

Do you notice any difference in the appearance of the spark plugs?

I would check the carbs. Make sure the throttle plates are closing fully and at the same time.

If any spark plugs appear oily, I would check the oil drain hose and fitting that is draining the oil from the crank bearing above or below that piston.

Another possibility is that the stator is not working properly at low speed. Check the A/C voltage output at the blue, red, blue/white, and red/white wires at the terminals on the switchboxes. Check each wire separately. Ground the black test lead from the multimeter.

Check the resistance also, red with red/white; blue with blue/white. You must disconnect the wires for this test.

Tony"
 
I would suspect that the comp

I would suspect that the compression is too low to adequately compress the air fuel mixture at Idle. Thus causing the build up of fuel and exesive smoke.
 
carburetor flooding due to a

carburetor flooding due to a bad float valve ???? Ruptured diaphragm in the fuel pump????
 
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