Get a new tachometer?

[BrianD1973]

'86 Cheetah 19ft 170 Merc... tach hasn't worked for years... needle is sitting in the bottom of the gauge :-( For prop experimenting and probably for just all around good maintenance and observation was wanting to get a new gauge for the dash... looking under there it looks like a ton of wires going to a Medallion Tach? upon further viewing, it seems maybe a connection board? (0.5"x3.5") is just attached to the U-clamp holding it in the dash... I guess for simplicity I could just get one of those little tiny tachs that I think just wind around a plug wire and spill out the tach info but would it be possible to just get another 3.5" tach and put it in the dash without messing something up? I think I've seen some info about a tach can be a source of ignition problems? I'm thinking if I remove the two nuts holding the U-clamp that the separate connection board will be free and need to be grounded somewhere? Guess if it gets used for a new tach that slips in the old one's spot then we will be good but wondering if the hook up for a new one would match with this connection board stuff I'm seeing... lol Boy, what a mess of thoughts! Just don't wanna screw something up and have no info on what I'm looking at...

 

[Eric 3.7LX Alpha 1]

Re: Get a new tachometer?

The tachometer only needs 3-wires to it.... 4-if you want it to light up.

(+)12volts from the ignition switch
(-) ground from the battery (could be coming from a terminal block where all are grounds)
and the signal from the engine... IT SHOULD BE a grey wire which runs back to the (-) terminal of the coil.

If you want it to light up you need to power the light bulb in it with the switch that will illuminate your other gauges.. But that one is not necessary for the operation of the gauge.

 

[NHGuy]

Re: Get a new tachometer?

You should just get a boat dash tach. They can be cheap, shop around. And yes there is an electrical connection that the tach is part of. You need either a tach or a connection in it's place. If that wire isn't there the motor won't run.

You could also just leave the wiring as it is and get a $13 tiny tach clone from e-bay.