Motormeters&reg; Essential Water Proof Hour Meter / Service Gauge for Dirtbikes Go-karts, Boats, ATV Jetskis (Blue) Works on Any Gasoline Engine. Track the Service Life of Your engine - oil changes, valve, adjustments, spark plugs, etc... No Battery Required - connects to spark plug wire. Marine Grade Water Proof Design Easy Installation - peel & stick, no wiring necessary, or attach with enclosed hardware.