Old OMC Tach Wiring Color Codes

[jbing81]

I have an old OMC tach that was given to me. It has 4 wires out the back, Blue, Black, Violet and either a gray or a brown??? The latter is faded so its hard to tell. Anyone know which is the pulse, 12v and gnd? Im assuming the forth is for backlight which Im not concerned with.



Also there is a dial on the back of the tach that lists 2,3,4,6 and H. It is pointing at the "6". Where should I have it If connecting it to a '77 Mariner 85 hp motor?

Thanks a lot!

Jeff

 

[jusfloatin]

Re: Old OMC Tach Wiring Color Codes

Also there is a dial on the back of the tach that lists 2,3,4,6 and H. It is pointing at the "6". Where should I have it If connecting it to a '77 Mariner 85 hp motor?

Thanks a lot!

Jeff

My bet is to set it the same amount of cylinders the motor has, not sure what the H setting would be for.

 

[seabob4]

Re: Old OMC Tach Wiring Color Codes

Blue= Back lighting
Black= Ground
Purple= Ignition Power
Gray= Tach Sender

The numbers are your "Pole" settings. I'm guessing 3 or 4. You can always set it on, say, 3, take the boat out, and run the motor up to WOT. You should see around 5K on the tach. If not, reset until you do...

 

[jbing81]

Re: Old OMC Tach Wiring Color Codes

Thanks Seabob!

That's how I hooked it up. I wasn't sure but I found enough info on the web to piece it together.

Thanks again!

 

[jbing81]

Re: Old OMC Tach Wiring Color Codes

So I hooked up the tach today and when the ign. was turned on all I received was a small jump out of it. I tried all the settings on the back and nothing... This tach is pretty weathered, old and sun baked. Could it be that the tach is just junk? Or could there be something else going on here? I have to pick up a new impeller tomorrow from the local shop so if a new tach is needed I might as well buy one of those also if needed.

 

[seabob4]

Re: Old OMC Tach Wiring Color Codes

There is also a good possibility that your OMC tach may not be compatable with your Mariner (probably a Merc motor). The voltage on the gray wire should be around 5V+. See if you have that. If so, and you've tried all pole positions, then either it's not compatable, or it's junk...

 

[jbing81]

Re: Old OMC Tach Wiring Color Codes

Turned out it was a pile of junk lol. On a whim I picked up a new one at the shop today (had a close out sale, only $35!). Installed it and it works as it should now. Only problem is the chrome mount it came with makes everything else look dull... Lol. Now I have some polishing to do! It never ends... =)