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Mercarb off idle stumbleFinally Solved

T

totomax1

New member
"Been working a annoying off i

"Been working a annoying off idle stumble on a 96 4.3L with 2 bbl mercarb. After numerous times into the carb, cleaning, playing with different float levels and accelerator pump strokes, I finally found the problem. One of the small brass tubes (.010-.015 id) that feeds the venturi cluster was plugged. Took 10X magnification to find it. I've read all the cautions about "probing" the small passages in carbs but the only thing that cleared this was a small straight pin. My "lesson learned" here is that if you think you are good at automotive carbs, marine application carbs can offer a new set of challenges."
 
"It's a PIA carb but easy

"It's a PIA carb but easy to work on. If you have a fuel/water separator filter, you can empty the filter and fill it w/SEA FOAM and run the engine for a few minutes to fill the carb with SEA FOAM. Let the engine sit a day or two and start it up. SEA FOAM will clean every internal passage like new. I use it w/every other 30 gal. tank of fuel. It keeps varnish and gum from forming while preserving the fuel.

They also make a product called "SLOW CREEP" which I use on all my engine carbs that need cleaning. It is thicker and dissolves problem plugs like you had. I used it on the carb bowl this last summer to clean out all the internal passages.

If your mixture screw does not respond quickly when adjusting the mix, get a 1/4" base gasket from a Merc. dealer and it will work perfectly."
 
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