Yanmar Pleasure Boat Marine Engine Help

Tachometer

There are several different types of instrument panel available. The older type is a black plastic fascia with round connecting plugs and the newer type has a GRAY FASCIA with oblong shaped CONNECTORS.Recently (2004) on some GM series and all YM and JH4 series a new Yanmar/VDO instrument panel has been introduced. These latest Yanmar/VDO panels have a combined VDO tacho & LCD digital hour meter, the VDO electronic tacho is adjustable and operates from the flywheel sensor on GM series and from alternator pulse on other models.
If the tacho is playing up it is most likely the connector on the engine. Pull it apart (the one with the blue/red and orange wires), spray with CRC / WD40 etc., shake out the excess and reassemble. Do the same with the connectors at the sensor on the flywheel housing.
If the wiring has any corrosion on it, replace the entire loom as the corrosion travels up the wire where you can't see it.