1992 Mercruiser 454 Magnum backfiring/popping

[Freedom9811]

1992 Mercruiser 454 Magnum, freshly rebuilt three summers ago with less than 20 hours.
Back firing / popping at 2000 rpm coming from left bank exhaust.

I have already replaced and checked the following this year to resolve this issue with no luck:
Compression tested all cylinders
Spark plugs
Wires
Cap
Rotor
Coil
Ignition sensor
Fuel filter
50 gallons fresh high test
Took apart carb, fully cleaned
Pulled exhaust manifold and valve cover and checked all movement of values and pushrods, all okay.

This season I haven't messed with timing, timing was fine. Could the initiation module be causing this. It's the last
thing I can think of replacing. I have read about tachometers causing problems, I do have graftion garages, which were installed at the time the motor was rebuilt three years ago.

 

[Bondo]

Re: 1992 Mercruiser 454 Magnum backfiring/popping

1992 Mercruiser 454 Magnum, freshly rebuilt three summers ago with less than 20 hours.
Back firing / popping at 2000 rpm coming from left bank exhaust.

I have already replaced and checked the following this year to resolve this issue with no luck:
Compression tested all cylinders
Spark plugs
Wires
Cap
Rotor
Coil
Ignition sensor
Fuel filter
50 gallons fresh high test
Took apart carb, fully cleaned
Pulled exhaust manifold and valve cover and checked all movement of values and pushrods, all okay.

This season I haven't messed with timing, timing was fine. Could the initiation module be causing this. It's the last
thing I can think of replacing. I have read about tachometers causing problems, I do have graftion garages, which were installed at the time the motor was rebuilt three years ago.

Ayuh,.... Recheck the firin' order, 'n the spark plug wire lay-out,....

 

[Freedom9811]

Re: 1992 Mercruiser 454 Magnum backfiring/popping

I have checked the firing order a few times.

 

[Bondo]

Re: 1992 Mercruiser 454 Magnum backfiring/popping

I have checked the firing order a few times.

Well,... It worked til ya fixed it, so, something ya did, Ain't Right,....

You said ya cleaned the carb,..?? What carb,..??

Maybe 1 side of it is plugged,...

Either Bad wire lay-out/ firin' order, or a lean condition are the most likely suspects,...

 

[Freedom9811]

Re: 1992 Mercruiser 454 Magnum backfiring/popping

Well after all that work I put a differant distributor on it to check it. It ran fine. So went and got a new ow made for boats. So I guess the ignition modular was bad. So all the run or not run stuff it not all true. I could not get it timed with old distributor. So if any body need a good distributor with a new ignition sensor let me know I have no need for it.