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Disconnect battery during installation, tighten nuts slightly, and avoid over-tightening.
1. Locate tachometer 18” from magnetic compass, avoiding interference from radio transmissions.
2. Use 18AWG stranded, insulated wire for connections, except for the light, which requires a 1/4” insulated female blade terminal.
3. For diesel, use a sender (90901 or equivalent) mounted to the engine, and one sender can operate two tachometers.
4. Set the selector switch to match the engine’s tachometer drive take-off ratio using a small screwdriver.
5. Mount the tachometer with the backclamp supplied after cutting a 3-3/8” dia hole in the dash.
6. Connect the tachometer to ground, battery, and signal, securing with nuts and lockwashers.
7. Connect the signal wire to the diesel sender or alternator signal output.
8. Connect the lighting circuit to the positive side of the boat’s instrument lighting.
9. Reconnect the battery, then calibrate the tachometer by running the engine at a known RPM and adjusting the pot until the tachometer agrees with the known RPM.
10. Replace the adjustment pot weather seal plug to complete calibration.
Note: To change the light bulb, twist the socket assembly counterclockwise, and for hourmeter-equipped tachometers, the hourmeter will be energized when the engine is running.