need help with tachometer connection

[ernstudet22]

I have a 1978 175hp merc. I bought a faria euro 8k tach. The pole setting options are 4, 10, 12 and 20. Will this tach work with my motor or do I need a 6 pole option. In addition, where does the signal wire connect on the motor? Thanks

[j_martin]

It's a 12 pole stator, (6 cycles per rev). If you have a regulator type system,it hooks into the grey wire off the regulator (either one on a 40 amp dual reg). On a diode system, it hooks into either yellow wire.

hope it helps
John

[ernstudet22]

How can I identify a regulator system vs. a diode system?

[j_martin]

The diode system has a diode mounted on the starboard side, on the switchbox plate. It has 3 screws, with 2 stator wires going to 2 of them, and the red battery wire going to the third. The tach wire goes with one of the yellow wires.

The regulator systems are varied. They either have a grey wire hanging out of the module(s) that goes to the tach, or a tach terminal on the regulator.

Poles are the same no matter which.

hope it helps
John

[sho305]

J Martin knows much more than me, but most of the older ones had a wire/plug on the controls for a tach or in the factory key wire loom if you have it. Or you can still hook it at the motor of course.

[j_martin]

J Martin knows much more than me, but most of the older ones had a wire/plug on the controls for a tach or in the factory key wire loom if you have it. Or you can still hook it at the motor of course.

It's grey. if you look at the motor and the grey wire is already attached where I said, look at the instrument wiring for an unused grey wire coming from the instrument connector on the controls.

john

[ernstudet22]

I checked it last night. It has the diode rectifier. There are the 2 yellows and battery positve as you said. It also has a brown that is piggy backed with one of the yellows. The brown goes up the the harness socket on the the control box for local hookup. I don't have the harness so I guess I'll connect at the motor.