ABYC Boat Wiring Color Codes

ABYC color codes assign a function to each common marine DC wire color so you can identify a circuit before you cut, splice, or replace it. Use the chart on this page as a reference, then confirm the actual boat wiring and circuit protection before you change anything.

What are the color codes for marine wire?

On boats that follow ABYC practice, colors map to jobs: red is the DC positive feed, black or yellow is the DC negative/return, and other colors mark lights, pumps, ignition, and trim circuits. Read the full table below for each color and typical use.

What color wire is positive on a boat?

Red is the usual ABYC color for DC positive mains (the + / L+ feed). Do not assume every red conductor is unfused battery positive — check the breaker or fuse and the device end before you work on it.

What color is boat ground or negative?

Black or yellow is the usual ABYC color for DC negative / main return. Many boats use yellow specifically to avoid confusing black DC return with AC hot. Follow the color already installed on that vessel unless you are rewiring the circuit to a documented standard.

What is ABYC wire?

People say “ABYC wire” when they mean marine-grade boat cable used with ABYC color and installation practice. Look for marine insulation, stranding, and (when specified) tinned copper. Match gauge, conductor count, and color to the job, then open the matching CLR Marine listing.

How should a boat DC circuit be color-coded?

Keep one function per color on that circuit, protect the positive feed, and land the return on the documented negative. Use the table below for starter, ignition, blower, bilge, nav-light, and trim colors. Shop tinned marine wire and terminals on this site after you know gauge and color.

Marine wire · Terminals · Ancor · Search by gauge, color, SKU, or MPN

Color Wire to Use

On this Item

That Use

Black

Ground

Negative / Neutral Main Return

Blue-Stripe

Tilt up and or trim out

Tilt and or trim circuits

Brown

Alternator Charge Light

Generator Terminal or Alternator Auxiliary Terminal to Regulator

Generator Armature

Generator Armature to Regulator

Pumps

Circuit Breaker or Switch to Pumps

Brown w/Yellow

Bilge Blowers

Circuit Breaker or Switch to Blower

Dark Blue

Cabin & Instrument

Circuit Breaker or Switch to Lights

Green or

Bonding System

Grounding Wires (if insulated)

Green w/Yellow Stripe

Green Stripe

Tilt down and/or trim tab

Tilt and or trim circuits

Grey

Navigation Lights

Circuit Breaker or Switch to Lights

Tachometer

Tachometer Sender to Gauge

Lt. Blue

Oil Pressure

Oil Pressure Sender to Gauge

Orange

Accessory Feed

Ammeter to Alternator or Generator

Common Feed

Distribution Panel to Accessory Switch

Feed

Accessory Circuit Breakers or Switches

Pink

Fuel Gauge

Fuel Gauge Sender to Gauge

Purple

Ignition

Ignition Switch to Coil & Electrical Instrument

Red

Power Feeds

Positive Main Power (particularly un-fused)

Instrument Feed

Distribution Panel Electrical Instruments

Tan

Water temperature

Water temperature sender to gauge

Yellow

Generator Field

Generator to Regulator Field Terminal

Yellow

Ground

Negative / Neutral Main Return

Yellow w/Red

Starting Circuit

Starting Switch to Solenoid

ABYC Marine Color Wiring Guide

Outboard Boat Engine Wiring

CLR Marine recommends using marine type wire from Ancor Wire, as the wire is tinned to help eliminate corrosion. Don't forget to use the proper Wire Connectors and Wire Terminals. Now that you have your wire ready don't forget about Wire Management. Do you need Wire Tools, such as Crimpers how about Heat Shrink Tubing which can also be found in Wire Management.

Wire / Conductor Sizes

Length (feet): Determined by measuring the length of the wire from the positive (+) power source connection to the electrical device and back to the negative (-) power source connection. Note that the power source connection may be the battery, panel-board or switchboard.

Current (amps): Determined by adding the total amps on a circuit.

Wire sizes not covered in Table C or Table D may be calculated by using the following formula:

After calculating the Circular Mil Area (CM), use Table B to determine the proper conductor size. The National Fire Protection Agency and Coast Guard require that the next larger conductor be used when the calculated CM area falls between two conductor sizes.

CM=K x l x L / E

CM = Circular Mil area of Conductors

K = 10.75 (Constant representing the mil-foot resistance of copper)

I = Current - amps

L = Length - feet

E = Voltage drop at load (in volts)

For Example:

Q. A bilge pump draws 10 amps. The positive run is 11 feet from the power panel, including the float switch. The negative run is only 10 feet. What size wire?

A. Use the following formula to reach the correct answer:

CM = 10.75 x 10 (amps) x 21 (total length of run) / 0.36 (3% of 12v) = 6,271

The table below shows that 12 AWG wire has a CM area of 6,500 and is the correct choice. However, SAE wire has a CM area of only 5,833. Under NFPA and USCG regulations, 10 SAE wire must be used.

CM = 10.75 x 10 (amps) x 21 (total length of run) / 0.96 (3% of 32v) = 2,352

Ampacity is the ultimate safe current carrying capacity of the wire before damage occurs to the insulation, without regard to voltage drop. Because the insulation of most SAE wire types is not the same as ANCOR, this chart should not be used for other conductor types.

AWG	Sq. mm	AWG CM area	SAE CM Area	Ampacity Engine Space Outside	Ampacity Engine Space Inside
18	0.8	1,600	1,537	20	17
16	1	2,600	2,336	25	21
14	2	4,100	3,702	35	30
12	3	6,500	5,833	45	38
10	5	10,500	9,343	60	51
8	8	16,800	14,810	80	68
6	13	26,600	24,538	45	38
4	19	42,000	37,360	160	130
2	32	66,500	62,450	210	178
1	40	83,600	77,790	245	208
1/0	50	105,600	98,980	285	242
2/0	62	133,100	125,100	330	280
3/0	81	167,800	158,600	385	327
4/0	103	211,600	205,500	445	378

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