My 1987 2.5 omc engine continuously fouls the plugs. The plugs run great for 60-90 minutes and then the engine bogs and the plugs are coated with dry black soot. The problem does not appear to be oil leakage into the cylinders because there is not oil loss and no smoke. I rebuilt the carb, replaced the plug wires, points and condensor, distributor cap and the coil. Dwell and timing are great after new plugs are installed. Could this simply be a low octane no-lead gas issue? Help?
