Boat / Marine wiring color codes

What color wire should you use on your boat, and is it important?  First of all: YES it is important.  Just like in your house, using the incorrect color wire when re-wiring your boat will be confusing to anyone working on it in the future and risks short circuits (or faults) that could cause serious damage to you and your boat.

In most small boats there are two main types of power distribution cable... 12Vdc positive, and 12Vdc negative, or + and -.  The colors you MUST use to identify the difference between these + and - are red and black respectively... I repeat:

Positive (+) = RED
Negative (-) = Black (or yellow)

Also, DC grounding conductors should be green... but for many small boats you will not have any grounding conductors on your boat.  These color codes are established by the American Boat & Yacht Council (ABYC), and are standard throughout the industry.  Please, don’t buy all one color wire to re-wire your boat.

Also note that the ABYC has established a more detailed standard of more than 10 different colors to identify what type of positive wire you’re dealing with.  Brown for instance should be used for all pumps, and Pink should be used for a fuel gauge.  These are recommendations only, not Coast Guard regulations, and while useful… having to buy 15 different colors of wire for a DIY job may be impractical. 

So remember… Red is + and black is –

Excerpt from ABYC standard E-11 “AC and DC Electrical Systems on Boats” :