The wiring diagram of a tachometer is used in conjunction with the engine's diagram to install a tachometer, which is a device that displays revolutions per minute (RPM). Wiring diagrams for tachometers vary, but they typically contain an ignition switch, light, instrument ground and tachometer sending wire.
Tachometers measure the rotational speed of an engine or other rotating machines. Since the wiring of a tachometer depends on the type of engine, the wiring diagram differs based on the type of engine.
A simple tachometer for a boat typically has three wires, a cylinder switch and a light detailed on the diagram. The device and light are powered by the wire, which connects to the ignition switch on the engine. The "G," or ground terminal, connects to the instrument ground wire of the boat. The "PUL" wire connects to either the engine's alternator or the ignition system, depending on the engine.
A common tachometer built for an eight-cylinder engine is very similar, but it has a few additional wires on the diagram. One wire connects to a light on a dashboard, and another connects to the fuse box. If the tachometer does not have a calibration switch, it usually has one or two clippable wires that calibrate the instrument for smaller engines.