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Author Topic:   Wiring an OMC Voltmeter
ratherwhalering posted 05-17-2006 07:27 PM ET (US)   Profile for ratherwhalering   Send Email to ratherwhalering  
Hi, I have an OMC voltmeter gauge, TECH series. It has two terminals on the backside labeled S and I. I know the ignition (violet) wire and black ground are to be used, but where? (I have the light figured out.)
Joe Kriz posted 05-17-2006 08:53 PM ET (US)     Profile for Joe Kriz  Send Email to Joe Kriz     

I think you better look at the back of the gauge again....

There are 4 terminals on OMC volt gauges that I am aware of..

1. I = Ignition

2. G = Ground

3. S = Sending Unit (I believe)

4. Unmarked = Light

You put the Purple wire, I had Violet, on the I terminal...
You put the Black wire on the G terminal
And if you want lights, the Blue wire goes on the Unmarked terminal where the screw in light socket is...

The S is not used for this gauge as it does not need a sending unit. If you have a trim gauge, look at it and there is a wire from the trim tilt sending unit hooked up to the S terminal

Chuck Tribolet posted 05-17-2006 08:55 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet
has the OMC coding, and I for Ignition makes sense, but S for
Solinoid doesn't. I can't find my manual or I'd check it for

Hey JimH: you should add that letter code info to your
wiring color codes page.


ratherwhalering posted 05-17-2006 09:15 PM ET (US)     Profile for ratherwhalering  Send Email to ratherwhalering     
Ah, thanks fellas. Joe it does have 4 post terminals, marked as you described. The S terminal had me "Stumped", and I thought it might be the ground for the voltmeter. It makes sense that the light and the meter share a common ground. I'll ignore the S terminal and wire it accordingly.

Thanks again, and if you get a chance, Chuck, let me know what the manual says. It seems odd they'd have a useless terminal, nut and all.

Joe Kriz posted 05-17-2006 09:39 PM ET (US)     Profile for Joe Kriz  Send Email to Joe Kriz     

Maybe that is what the "S" terminal stands for "STUMPED"...

I have wired plenty of boats with OMC... That is my specialty and preference in Outboard motors...

Think about this, they use the same mold to make many of the 2" gauges. The Voltmeter does not need a sending unit like many of their other 2" gauges. So, the "S" terminal is not needed for the voltmeter.

I just finished rewiring my 1989 Outrage 22' Cuddy and all the gauges are the OMC Tech Series... Lucky You.... and me...

All my gauges now work with the exception of the trim & tilt gauge. I tried two different gauges which I have in stock and are brand new... Lucky Me... Unfortunately there is either a problem with the "S" wire or the Sending Unit itself... I suspect the sending unit on this 1999 Johnson...

Many people have no use for the trim & tilt gauge... Well, I wouldn't be without one... Maybe I am too lazy to turn around to see where the engine is at a starting point. I know when I get on "trim" as you can hear the tone of the engine, and the boat for that matter, but I want to have a visual upfront....

Manuals... The first thing anyone does is throw those things away, don't they? :-)

jimh posted 05-17-2006 11:35 PM ET (US)     Profile for jimh  Send Email to jimh     
I don't know what the "S" stands for--that's why I was staying out of this!

A voltmeter just needs the ground and the input voltage. Getting the input voltage via the "I" (for ignition) terminal means the meter only reads when the ignition switch is in the RUN or START position. That makes sense. That is the VIOLET (or Purple) wire.

About the only purpose for the extra terminal "S" is perhaps an isolated ground return to the battery. In that way the meter will not be affected by ground currents for other equipment connected to the ground buss at the helm. It would improve the accuracy of the meter. But that is just a guess.

Chuck Tribolet posted 05-17-2006 11:40 PM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
I just went out and looked at my OMC voltmeter. S is not
connected. I think Joe has it right.


Joe Kriz posted 05-18-2006 01:06 AM ET (US)     Profile for Joe Kriz  Send Email to Joe Kriz     
I like to make light or lite of things at times because the world is full of it...

On a Serious note:

S stands for Sender or Sending Unit

If you look at any of the other gauges that use the "S" terminal, the wire that is hooked up to this S terminal comes from the sending unit or sender.

Now, not so serious...

"S" stands for Smiddy or Schmidty or Smitty... Right Rob Schmidt?

ratherwhalering posted 05-18-2006 02:37 AM ET (US)     Profile for ratherwhalering  Send Email to ratherwhalering     
Let me start by saying...Holy Guacamole Joe! That is a sweet rig. It looks 10 times better than the original photos. BTW, save the plastic arm from the old trim sending unit. The BRP replacement arm is different, at least it was on Brian's OMC 1991 150Hp. The old one slipped right on the new unit's shaft. Everything else fit like a glove.

Before I started this thread, I thought 'S' stood for SHOULD ask ...this is my third Tech series voltmeter! When I researched the reference section, I found Table 1. Boston Whaler Wire Color Code for DC and Special Circuits, after a similar table from Whaler.

02 Blk/Red Voltmeter Grounds

from the reference section

This is why, as Jim suggests, I thought it might be for an isolated ground return to the battery. That makes sense too...kind of like the black with tan ground for the trim/tilt gauge. That took me three tries too. I'll perform a little test. I'll connect the 'S' to the ground, the 'I' to the ignition, and see if it works. If not, I'll connect the light (blue wire) and the common ground (black wire).

Chuck, thanks for looking, I appreciate it. I'm still going to experiment, as above, just to see. If it is a dead terminal, nothing should happen, right?

Next time I'm buying from my OMC dealer, installation guide and all...not E-Bay.

swist posted 05-18-2006 08:52 AM ET (US)     Profile for swist  Send Email to swist     
I've always hooked DC positive (red) to the voltmeter rather than ignition (purple). I think it gives you much more information - you can see the state of your battery when the engine is not running - if you are running accessories with the engine off, this is useful information.

The meter does not draw sufficient current for this to drain the battery in and of itself.

I do realize, however, that most people use the ignition wire as input.

Joe Kriz posted 05-19-2006 08:01 PM ET (US)     Profile for Joe Kriz  Send Email to Joe Kriz     

Thanks for the tip on the arm for the trim & tilt sending unit.
I will remember that as I am going to order the sending unit soon.
I won't throw the old one out as some other people do that I know of... :-)

The Cuddy is coming along nicely... Thanks...
I feel much better now that I have gone through all the electrical system and installed the voltmeter which is the only gauge that I felt was missing and that the boat needed. You can view the page of the boat and see all the instruments that it has including a water temperature gauge and oil tank level gauge. I have never had the oil tank level gauge as never really needed it, but now that I have it, it is really kind of cool.

ratherwhalering posted 05-23-2006 04:50 PM ET (US)     Profile for ratherwhalering  Send Email to ratherwhalering     
Connecting the ground to the S terminal resulted in nothing happening. Connecting the Ground to the G wire gave full function, instrument and light. So it looks like it is indeed an unused terminal post.

Thanks for the responses, and hopefully this will be the last voltmeter I have to install.

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