Looking for a new tach

[teslaman]

I would like to purchase a new tach for my johnson 73 115hp. Can I simply purchase any teleflex tach for outboards to use for my motor, or do I need to select on specifically designed to recieve pulses from the 73 115hp? Does the new tach need calibrated? If so, how do you calibrate?

 

[ezeke]

Re: Looking for a new tach

Either the OMC/BRP or Teleflex have the same settings and you would set yours to 6p,

You will want a single purpose guage with standard wiring [threaded posts] rather than the 8 pin ones that go with a System Check guage, unless you want to upgrade the wiring system.

If you have the OMC control with the black leatherette top, the wiring can be pulled from there.

The gray pulse wire is inside of the control, taped off. The other two wires are attached to the ignition switch.

 

[teslaman]

Re: Looking for a new tach

I have an old tach which is wired from the gray wire, but for some reason it stopped working. I've checked the wiring and the tach gets power, I've also installed a new rectifier but that didn't fix the problem either. When I started the motor last week I noticed that the needle worked sometimes and not others. When I tapped the back of the gauge the needle would respond, so it looks like a problem in the old gauge. I think that simply installing a new unit would fix the problem.

Thanks for the help!

 

[ezeke]

Re: Looking for a new tach

It is possible for a rectifier to have a bad diode and still be partly functional. Check the rectifier first before you invest in another tach.

Disconnect the rectifiers wires and then check each wire with an ohmmeter switching polarity and using the rectifier's case as ground You should have flow, but only in one direction.