Engine backfire

[Don annis]

Hi Fellows,
Have 2000 SR 2100, 5.7 Thuderbolt, 250 HP,
2 BBL. After towing tubers for an hour, turning back and forth. Started getting
popping/ backfire at about 2000 RPM. Above that range seemed OK. RPM’s seemed to register a little high for the speed on the way back. I’m truly lost. Could it be sticky float from cutting back and forth? Does it sound electrical? Has 260 hrs on the motor. Think all is original. Bought used.
Had it out 7 times since last July. Any help would be greatly appreciated. Thnx
Don

[Gugi47]

Welcome aboard.
Can be more than one problem.
You losing power when you have the backfire?
Water in gas, rebuild carburetor, getting water true manifold.
I just have the last one. I have to change the manifold and the problem when away.

[mmwjr]

Welcome aboard

Did you ever have the engine tuned up? Spark plugs, distributor cap, rotor, wires?

If not start there.

[jrsick]

Concur with Mike's tuneup advice. Your problem sounds like an ignition issue.
Check the plugs when you pull them and see if they are wet.
Also check inside of distributor cap for moisture.

[Don annis]

Thanks, I was leaning toward ignition also.
I’ll get the tune up and go from there.

[jrsick]

The last time I heard of a boat with the symptoms you describe, the problem turned out to be the distributor cap.