or two years now my 1979 260 merc with omc 800 (5.7)chev engine. The engine backfires through the intake at cruise speed. never at slow speed or idle. only loaded. some times i can throttle past it but mostly i have to reduce power to clear it or it will just keep popping. i have gone over or changed evything IE: ignition, cap rotor wires plugs distributer and coil. fuel system checked pressure and volume. changed the carb, two filters and water sep. have changed the cam, lifters and timing chain. have powered the ignition off the battery direct and eliminated the tach and all other wiring. have checked fuel for seperation and water. compression is perfect and so is the timing and advance also new manifolds. old hrisers any thoughts would be greatly apreciated. thanks in advance steven
