View Full Version : Fluctuating RPM

07-17-2007, 09:18 PM
"I have a 1992 454 marine power sport PAC 320 HP. RPM’s fluctuate by about 300 to 400 rpm lower. Will run that way for anywhere from 15 to 30 seconds than return to the RPM I set the engine at. Will continue to run this way as long as the engine is running. Never increases in RPM.
We have replaced the external fuel filter and cleaned the filter at the carburetor. A rebuilt carburetor was installed and solved the problem for awhile. We have also replaced the plugs, wires, distributor cap and rotor. This engine does have an electric fuel pump.
Boat has a single fuel tank and the other engine is running fine.
Would appreciate any suggestions to the problem anyone might have.


07-20-2007, 12:03 PM
Suggest adding a METAL in-line can type filter before the carb and after the fuel pump. Those tiny in-carb filters have low capacity and have ruined many a motor.