96 OMC 5.0FL Backfiring

[96Seaswirl]

Hello, looking for proven solutions to a recent symptom. My 96 OMC 5.0 FL, carburated, started backfiring and would not get on plane. I checked water separator-no water, compression-all good, air gap in distributor-good, timing?, has new tank of fuel.
One mechanic says definitely fuel delivery related, another says ignition related. Which mechanic to choose? Anyone actually solve this problem?

 

[JustJason]

Re: 96 OMC 5.0FL Backfiring

What are your actual compression numbers?
Have you checked your base and advance timing, what are the actual numbers?

Could still be fuel related, you can try hooking up a temporary 3 gallon outboard fuel tank with fresh fuel and see if it still does it.

I do my troubleshooting for bad running engines in this order.
1. Mechanicals - Compression
2. Ignition system - Spark and spark advance
3. Fuel system - Fuel delivery first then on to the carb/efi system

It works best if you do it like that, if you jump around one usually makes a mistake.