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91 43 Merc high speed suddenly drops

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fireman_brian

New member
"My 4.3 runs great for couple

"My 4.3 runs great for couple hours, then it suddenly drops from about 4300 rpm to 3000 rpm. Has stalled once but usually just falls. Pull back on gas to slow down and will run okay at 10-15 mph at 3000 rpm. Did tune-up w/o wires. Replaced fuel vent weeks ago. When I slow down suddenly it seems like water might go into vent. Old vent had black plastic ring around it. New one just plain-jane. Love this site by the way. Very informative."
 
"fuel sep./filters maybe,float

"fuel sep./filters maybe,floating debris in the tank, anti-syphon fitting,
this carb or injected, running temp?"
 
Had the same problem but it wa

Had the same problem but it was my coil getting too hot. I also had somewhat of a vacuum leak in the carb from a dry rotted cap on one of the vacuum pipes.
 
carb. temp 130-150. pulled s

carb. temp 130-150. pulled sending unit and saw some debris in tank. not sure where anti-syphon valve is. I did notice a spark from one side of coil to center plug wire one time. has not done it since. checked the fuel filter and it was partially clogged. thanks
 
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