Mercruiser 4.3 V6 Backfire - HELP

[Bereforest]

I have just picked a 96 Bayliner with a Mercruiser 4.3 LX V6. Its been sitting for a while with 1/2 tank of fuel. Topped her up with 1/2 tank of fresh fuel. On a test run she was fine at all speeds. After 1hr boating at various speeds she developed a loud backfire which seemed to be coming from the carbs. It will idle and run at low speeds, but as soon as you throttle hard the backfire occurs. After inspecting the ignition the coil is arcing from the tower casing below the lead rubber to the + / - poles. After taking the coil out there doesnt seem to be any visible damage or cracks. Changed the coil leads but it still arcs. Can anybody shed any other light on possible causes. Could there be another cause for the coil sparking?

Any other possible causes for the backfire?

 

[cooter2506]

Re: Mercruiser 4.3 V6 Backfire - HELP

Coil leads? IM assuming you changed the spark plug wire from coil to the cap. Or did you change all of them? If you didnt I would change them all and perform a complete tune up. Change the coil. Change the fuel water seperator. Backfires thru carb is usually a lean fuel condition. You probably picked up some water from the fuel tank. From it sitting so long it probably got alot of condesation in it.

 

[Bondo]

Re: Mercruiser 4.3 V6 Backfire - HELP

Can anybody shed any other light on possible causes.

Ayuh,... It's because there's Too Much Resistence downstream of the Coil....Electricity follows the path of Least resistence,....
Everything downstream includes the Hi-tension wires, the Dist. cap, the Rotor,+ the Sparkplugs...
In other words,...
It's Way past time for a Tune Up,+ Service.....

I agree, changng the Fuel Filters will probably sort out the Backfiring...
'course, that's also a normal part of Servicing it......

 

[Bereforest]

Re: Mercruiser 4.3 V6 Backfire - HELP

Thanks. Is it likely that the coil could be ok, or worth changing it anyway?

 

[Bereforest]

Re: Mercruiser 4.3 V6 Backfire - HELP

Thanks. Is it likely that the coil could be ok, or worth changing it anyway?

 

[Bereforest]

Re: Mercruiser 4.3 V6 Backfire - HELP

Ayuh,... It's because there's Too Much Resistence downstream of the Coil....Electricity follows the path of Least resistence,....
Everything downstream includes the Hi-tension wires, the Dist. cap, the Rotor,+ the Sparkplugs...
In other words,...
It's Way past time for a Tune Up,+ Service.....

I agree, changng the Fuel Filters will probably sort out the Backfiring...
'course, that's also a normal part of Servicing it......

Is it likely that the coil could be ok? Or worth changing it anyway?