?????------You just need 1 tachometer.-----The tachometer you need will be driven by pulses from the battery charging coils in the stator.----Not the ignition coils at all !!!!
Your control box should have a three pin plug on the aft end. You'll need the female connector. Black lead is ground, purple is 12v, grey is the signal.
I just bought a Faria universal aftermarket analog Tach for about $50 new on Amazon for my 1989 Johnson 70. I just hooked up the gray wire from the control box to the signal post on the gauge (and of course 12V+/-) and set the selector on the back of the gauge for my engine. The setting has to do with the pulses per revolution. Worked great.
The paper that comes with it tells you how to set the pulse/rev correctly for most engine make, model, cylinders, year with a little dial on the back of the gauge.
Looks like they only support 1977 and newer for plug and play. If older than that, they have some rewire suggestions at the engine/rectifer. Here is the PDF:
I was scratching my head thinking, what the heck control is that.. I thought it looked like a late 80s TNT relay set up
what year is the OP's motor....some tachs are systems matched.. and have SLOW warning capacity, and have an 8 pin connector .... although they usually have a way to connect wires that are coming from a control that doesn't have an 8 pin lead
