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43L Popping Backfiring

M

Mike DeCarlo

Guest
1995 Larson 17.5' 4.3L
A

1995 Larson 17.5' 4.3L
After running for a while (45 minutes) she starts missing on the high end of the RPM spectrum (2500 +). I'm thinking the coil is breaking down but looking for confirmation. Up until that time she runs perfect.
 
"Mine does that, but only when

"Mine does that, but only when "sitting for a day" cold. Once it warms up it all is fine. Coil is a cheep place to start."
 
"It's More likely that the

"It's More likely that there's Crap in the Fuel Filter,+ it's Starving for Fuel......"
 
"i have a 1985 sea ray 28'

"i have a 1985 sea ray 28' twin 260 mercruisers.
port engine runs fine. starbord engine spits and pops.
when i get to 3200 rpm, were it is starting to plane, it starts to spit and pop and loose rpm. will run good at 1000 rpm . at 1500 rpm it will start to spit and pop. fuel lines, filters have been replaced. carb has been rebuilt. new distruber cap and rotary cap.
needless to say i need help."
 
"Does each motor have an alter

"Does each motor have an alternator? If so, when it starts popping, check the voltage going to that coil. A bad VR can cause over-voltage which results in sparks flying to multiple contacts in dist cap. Happened to mine. Good luck. JW in Dixie"
 
"Larry:

Welcome. Rather

"Larry:

Welcome. Rather than tagging onto someone elses problem, it is customary to start a separate thread so all can see your dilemna. Thanks"
 
"Just put back in the water af

"Just put back in the water after 3 years my parents 20ft Arriva with V-8 305....have put on new plugs,oil, oil filter, impellar, cleaned fuel filter, added new gas, runs great for about 30 minutes at high and low speeds, then she starts sputtering, backfiring,and the RPMs go low...can't go fast after that...I'm running out of thoughts of what else I should do...any help would be great as I'd like to enjoy the rest of this summer...this girl would like to enjoy the boat!
Lindalee ;-)"
 
"After it starts running poorl

"After it starts running poorly, try stopping the engine and then open the fuel cap. If you hear a loud hiss; that's your problem. Your fuel cell vent could be clogged, easy to check and fix. Fuel can't get to the motor because it's vaccum locked and working against itself. Worth a try..."
 
"Lindalee:

Welcome. Rather

"Lindalee:

Welcome. Rather than tagging onto someone elses problem, it is customary to start a separate thread so all can see your dilemna. Thanks"
 
can you watch the voltage at t

can you watch the voltage at the helm station to see if it is too much? also is the regulator internal?
 
"Yes, Bob. Your dash voltmeter

"Yes, Bob. Your dash voltmeter will tell the tale. Internal VR? Depends on which model you have. The older ones, like my 1979, had a flywheel alternator feeding into a water-cooled VR bolted to the port side of the block. My VR went bad, causing overvoltege and resultant backfiring. I bought a marine alternator with internal VR, one wire to Batt, and rigged it on the front of the motor, driven by a v-belt to the damper pulley. Aside from hatching up a bracket, the total cost was $105 for a brand new alt. The Merc VR is around $400. Phooey. Good luck. JW in Dixie"
 
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