Moderated Discussion Areas
  ContinuousWave: Small Boat Electrical
  OMC Color Codes: Wiring Gauges

Post New Topic  Post Reply
search | FAQ | profile | register | author help

Author Topic:   OMC Color Codes: Wiring Gauges
george nagy posted 05-08-2007 11:03 AM ET (US)   Profile for george nagy   Send Email to george nagy  
I hope to wire the guages on my 1998 Johnson this weekend. I want to make sure I have the color code correct.

Here is a list of guages to be installed and the wiring colors:

Guage lights

1. system check tach guage: ground=black; positive=dark blue

2. water pressure guage: ground=black; positive=dark blue

3. trim indicator guage: ground=black; positive=dark blue

4. hour meter: is it lighted?

The above colors are interpolated from a set of directions which came with the water pressure guage stating that ground be black and positive be dark blue. My assumption is that all OMC lighted guages have the same color code for lighting. I also assume that the positive lead is fed from the running light throw on the navigation light switch. Are these lights somehow controlled when the keyswitch is on? Are my color assumptions correct?

It has been a while and I don't remember how the hour meter is wired. Does anyone have a set of OMC instructions? The hour meter has two male tabs on the back but I'm not sure where the connect to.

Any help would be appreciated.

Thank you.

Whaler_bob posted 05-08-2007 11:56 AM ET (US)     Profile for Whaler_bob  Send Email to Whaler_bob     
Just added water pressure and engine temp gauges to my Montauk w/1992 Johnson 90hp last weekend. The gauge illumination wiring was as you described; black for common ground, and dark blue for power to the gauge internal lamps. The power for the gauge illumination can come from the accessory (violet color) lead from the ignition switch or a separate powered/fused switch in the dash, or even your nav light switch.

Most Hobbs (hour meter) gauges operate off the common system ground and accessory (violet color) lead from the ignition switch and are illuminated by the same leads. Some have a separate illumination terminal.

george nagy posted 05-08-2007 02:22 PM ET (US)     Profile for george nagy  Send Email to george nagy     
It makes sence to illuminate the guages only when the keyswitch is on. I think I will try to run the violet ignition lead through the navigation light switch so the guages will light only at night while the nav lights are on. Is this the way it is done usually?
DaveS posted 05-08-2007 03:23 PM ET (US)     Profile for DaveS  Send Email to DaveS     
I remember reading a couple of years ago that it was a good idea to keep your lights on all the time because the heat from the lights would prevent condensation from forming on the interior of the benzel...I think it was a forum member so I'll have to look for the thread...

Good luck...


jimh posted 05-08-2007 03:54 PM ET (US)     Profile for jimh  Send Email to jimh     
If your Boston Whaler has a compass which was installed at the factory it generally will have a switch which controls the compass lighting. This is a good switch to use to control all the instrument panel lighting. It is the "Whaler Way" of doing it.
jimh posted 05-08-2007 08:58 PM ET (US)     Profile for jimh  Send Email to jimh     
There is a listing of color codes for wiring for several manufacturers (including OMC) in the REFERENCE section. See

There is usually not a distinction made between a dark and light hue of a color. Blue is generally used for lighting circuits, including instrument lighting.

An hour meter may have a polarity. Look for a plus and minus sign to indicate the polarity, or else the meter may run backwards.

Chuck Tribolet posted 05-08-2007 10:08 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Don't bother routing the igntion switch accessory lead to
the light switch -- You won't be able to run the anchor light
with the ignition off.

There are two schools of thought:

Wire the gauge illumination to the purple wire. This runs
the lights whenever the engine is one and helps keep the
gauges dry inside.

Wire the gauge illumination with the red/green lights.
That saves the bulbs and runs the lights whenever you running
lights are on.


fuzzyb posted 05-09-2007 01:06 PM ET (US)     Profile for fuzzyb  Send Email to fuzzyb     
the ABYC color codes do reference dark and lite hues, however, it is often hard to find the variations in stores.
jimh posted 05-09-2007 06:06 PM ET (US)     Profile for jimh  Send Email to jimh     
In most industry practice there are standard wiring codes. Here is a good catalogue showing some of the more common wiring color standards. I do not recall any color chart standard using "light" and "dark" colors; it is much too subjective for a color coding. Belden makes wire for many applications and has an extensive lising of color codes used in their wires:

See: 22Technical%20Information_Glossary/22Technical_Information.pdf

Pages 22.17 to 22.19 list a few wiring color combinations used in standard cables--and none are "light" or "dark."

I cannot speak about what ABYC standards say because I have not purchased them. Because no one can see or read the ABYC standard here, we are down to a basis of "trust me, you will just have to take my word on it" for what the ABYC says about color codes. It would be much better to have a copy of the standard published than to make vague reference to what it says.

If anyone has an old standard they would like to send me, I would be glad to have it. Until I see it in a standard, I will stick with my original statement:

"There is usually not a distinction made between a dark and light hue of a color."

jimh posted 05-10-2007 12:57 AM ET (US)     Profile for jimh  Send Email to jimh     
A pointer to a secondary source of ABYC recommended practices shows that there is a recommendation for LIGHT BLUE and DARK BLUE wiring colors, as follows:


DARK GRAY = TACHOMETER (but no reference to a light gray)

A major manufacturer of hook-up wire shows the following colors available:

1 Brown
2 Red
3 Orange
4 Yellow
5 Green
6 Light Blue
7 Purple
8 Gray
9 White
10 Black
11 Tan
12 Pink
13 Dark Blue
14 White/Black
15 White/Red
16 White/Green
17 White/Yellow
18 White/Blue
19 White/Brown
20 White/Orange
21 White/Gray
22 White/Purple
23 White/Black/Red
24 White/Black/Green
25 White/Black/Yellow
26 White/Black/Blue
27 White/Black/Brown
28 White/Black/Orange
29 White/Black/Gray
30 White/Black/Purple
189 Green/Yellow
620 Green/min. 30% Yellow
876 Nickel Gray
B02 Purple

I suppose you could say that "pink" is really "light red," too, but that is a stretch. I don't know what the difference is between gray and nickel gray. Tan might be considered "light brown."



Belden Hook Up Wire Color Chart at 03HookUp_Lead_Wire.pdf
See page 3.29

george nagy posted 05-10-2007 10:07 AM ET (US)     Profile for george nagy  Send Email to george nagy     
I just bought a few feet of dark blue ancor 16 awg wire last night. I was about to start wiring the guages together and then I overtightend the hour meter and the lense popped off, oh well.
towboater posted 05-11-2007 02:02 AM ET (US)     Profile for towboater  Send Email to towboater     
great thread,
Thx Jim, your info saved me a lot of time...again.


jimh posted 05-11-2007 09:06 AM ET (US)     Profile for jimh  Send Email to jimh     
To summarize, the ABYC only calls for a light or dark variation in wire insulation color for a BLUE wire, and only in the case of a oil pressure sender as distinct from a general use for lighting circuits. Because the use of an oil pressure sender is very rare in outboard motor instrumentation, I think it is probably reasonable to cease to worry about the lightness or darkness of the blue insulation on the hook-up wire you might use for lighting circuits. It is extraordinarily unlikely that there will be any confusion regarding the purpose of a blue wire unless you happen to have an outboard motor installation with a oil pressure gauge. (Has anyone such an installation?)

There is much greater likelihood of confusion between the use of BLUE in the tilt trim system--it is common among many outboard manufacturers--and the use of BLUE in the lighting system.

Post New Topic  Post Reply
Hop to:

Contact Us | RETURN to ContinuousWave Top Page

Powered by: Ultimate Bulletin Board, Freeware Version 2000
Purchase our Licensed Version- which adds many more features!
© Infopop Corporation (formerly Madrona Park, Inc.), 1998 - 2000.