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Tachometer Wiring

That's the way to go.Up until late'70's or early '80's, the tach sig. was brown for Mercs.Thereafter it was grey.This was because of a standardization of wire colour coding throughout the marine industry.Yamaha do not adhere to the colour coding.Their tach wire is green.
 
OK. Installed new rectifier today. Attached tach wires and got no reading. Reversed and also got nothing. Could this tach be shot? Any other suggestions? How can you test a tach?
 
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Must be for 6 cylinder only. Got readings either all the way out or all the way down depending on switching wires. Will look to get new tach. One more question. I promise...the last regarding this...I've been looking at older tachs that allow 4 cylinders to be selected. They have a battery, ground, and signal connection. Should it be GRAY to SIGNAL, BLACK to GROUND, and RED to BATTERY?
 
You're welcome.
You must have bought the old merc tach the same place I did.:(Though when I hooked mine up it wouldn't go past 3000RPM's.
As my modern tach works set at 6P on my Merc800,which is '69,4cyl and the Merc tach is '78,I can only assume that the '78 tach is engine sensitive.
 
That's what I gather too. Bought mine off Ebay years ago for my in-line 6. Memory fails me, but seem to recall something about it being for 6-cylinder engines.

6P....OK. If not, I'm gonna hit you up for more info.
 
Haventaclue...purchased a new tach. Ran wire fro SGL to gray, GND to fuse block, LIGHT to my light switch, and had to run BAT to the purple wire as that was the one providing juice with the ignition switch. Had it originally set to 6 pole, but was reading over 2 grand at idle. !2 pole seems to be the right setting for my motor.

Thanks for all of your help.
 
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