Mercruiser 3.0 backfire

[gucio1]

Have 1992 Mercruiser 3.0. Have been tinkering with it for a while now. Last issue was a defective pentronix ignition coil. I have since replaced it and over all it has been running really well.

The new issue is a back fire when going over 4000 rpm. Not continues and not instantaneous but after running at 4000 rpm for 5 min or so you can hear a loud pop. It then runs fine for a bit and then another pop if I do not throttle down. If I have it around 3500 it runs no problem.\
Looking forward to your wise insights.

Thanks

 

[texans543]

This sounds like a timing issue. Check to see if the distro bolt came loose and it moving under load. Check your cap to see if any rust or corrosion is under there. look at your wires where they can be getting hot and arcing, then last what comes off my head it timing chain.

 

[Bondo]

Ayuh,..... Sounds like it might be a lean condition to me,.....

At those rpms, the motor is at maximum fuel burn,....

 

[Scott Danforth]

^+1.....what he said