Argh! Tachometer wiring, '94 70hp

[Beefer]

Ok, I think I'm going to go nuts trying to install a tachometer. The boat is a 1994 Bayliner Capri 16', with a 1994 70HP Force. Tach is a Teleflex. My problem is (at this point) figuring out which wire is the tach sending wire. Under the dashboard/console, I have 3 unused wires coming from the engine; 1) tan 2) Black w/white stripe 3) Grey w/black stripe. On the iginition, there is 1) yellow w/red stripe 2) purple 3) yellow w/black stripe (and a couple of others that I forgot the colors of).

I was told that if you hook up a test light when the engine is running, the one for the tach will have a pulse/strobe effect. The 3 unused wires did not light the test light at all, and I did not want to disconnect the ones from the ignition to test until I knew what each was for.

Does anyone know which wire is the tachometer sending wire? In the engine, I honestly don't know what I'm looking for, and most of the wires are in shrouds or what the connect to is not visible.

Anyone have any ideas?

 

[Frank Acampora]

Re: Argh! Tachometer wiring, '94 70hp

On the older Force engines, purple was the tach signal wire. This does not necessarily hold true after Merc got their hands on the engines though, and the 70 is different than the 85 and 120-125.

SO Look on the engine, probably on the starter motor mount, for the rectifier--a square black rectangle with 4 or 5 wires attached. If the purple wire is attached there, it most likely is the tach signal. Usually, the red and black wires are positive and ground The odd wire that attaches to one AC terminal of the rectifier will be the tach signal wire. That color should follow under the dash.

Since the tach operates off a 20 pole alternator and since the alternator delivers about 14 volts AC, use the AC side of your voltmeter to test underdash wires. A wire which shows 14-16 volts AC will be the tach signal wire. Since the signal wire attaches to the AC terminal of the rectifier, thus directly to alternator output, it should be delivering true AC and not just a 1/2 sine wave pulse.

On some control boxes with ignition switch in the box, there should also be a three wire cable coming from the control box to the dash. If I remember correctly, One of those wires (not the red, that's 12 volts DC) is the tach signal.

Sorry I couldn't be more definitive.

 

[kandil]

Re: Argh! Tachometer wiring, '94 70hp

On my force 120HP 94 it is the gray wire it could be the same for yours and for 90HP it is purple and I have a color chart for engine Wier code was posted her by justintime that I stapled to my shop manual it stated old force is purple and new (after 93) Force are gray good luck