It is the TachometerWould that be you tachometer or the knot meter?
ClaudeThat engine's tachometer is driven from a "tooth counter" pickup on the flywheel housing. It is just aft of the cylinder head and has two wires coming out. The usual problem is a bad connection in this counter circuit. The bad connection could be at the counter pick-up or in one of the two multi wire plugs between the engine and the tachometer itself. I've attached some information on the tachometer.