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Boat does not idle well

Tonislc

New member
I purchased a used boat and it will not idle for more then 10-20 seconds. It dies not like to run on low RPM. Its a carburated 4.3 vortec about year 1995. I have done the following replacement parts.
New fuel pump
New cap/rotor, wires and spark plugs
New trottle cable
Disassembled, cleaned and re lubricated trottle and shift control
Fresh tank of fuel with sea foam
New fuel filter
Oil change and new filter
It runs great at higher RPM
Any suggestions would be appreciated
 
There are deposits that form in carbs on engines run on ethanol laced fuel in a marine environment, that because of their chemical composition, flow right thru any filter, accumulate, and thendon't dissolve in carb cleaners. These deposits like to clog the low speed jet circuits. There are two ways to remove them: totally disassemble the carbs, remove the jets and chip out the deposits with a very fine wire, or numbered drill bit (by finger, not in a drill!!) smaller than the jet ....or.... dunk the carb in an ultrasonic cleaning machine for awhile. When this happens every couple of years on my boat, the symptom is that in a rather short period of time it goes from: idles OK, to... won't run under 1500 RPM at all.
 
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