Two station Tachometer issues

[donwhiteside]

Hello all- I have a '73 Cruise-a-home with a Mercruiser III with Mercruiser 325 engine. It has a Thunderbolt ignition system.

The tach at the downstairs helm station works fine. The tach on the fly bridge doesn't work at all. There are switches near the tachs, both top and bottom, that seem to be for changing the "signal" to top or bottom. When switched, the lower tach STOPS working, but the upper doesn't ever work. I've tried to put my ancient (1967 or so) Hawk Mini-Analyzer at the tach lead and get no reading, top or bottom. (It may not work with electronic ignitions) Anyway, suggestions about how to diagnose this problem? I'm assuming the switches near the tachs are sort of a "3-way" switch so the signal only goes to one tach at a time, therefore maintaining accuracy?

All suggestions welcome.

Thanks,

Don

 

[1730V]

Re: Two station Tachometer issues

Tachometers only need a few things to operate.

-Power
-Signal, from coil.
-ground
-power for light if eqiupped.

You are missing some if not all of those.

 

[I/O WALDO]

Re: Two station Tachometer issues

(Bad tach?) I think,thank,thunk that the tach ground and signal wires should be parallel in respect to each tach.Maybe the power is supplied via the "3"way sted of the ignition switches??Need a dependable test lite to test fur sure!

 

[mkast]

Re: Two station Tachometer issues

Switch the tachs. You can verify if it is a bad tach.