justanswerImage: justanswerThese are the most common colorcodesused in boatwiring. Black. Grounds,General. Black/Brown. Pump Grounds. Black/Red. Voltmeter Voltmeter A voltmeter is an instrument used for measuring electrical potential difference between two points in an electric circuit. Analog voltmeters move a pointer across a scale in proportion to the voltage of the circuit; digital voltmeters give a numerical display of voltage by use of an analog to digital converter.enpediaGrounds. Black/Orange. Standard Boat Wiring Colors - CP Performance Was this helpful?