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  MERCURY 50HP WITH YAMAHA TACH?

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Author Topic:   MERCURY 50HP WITH YAMAHA TACH?
nod posted 07-24-2008 06:30 PM ET (US)   Profile for nod   Send Email to nod  
HI I HAVE RECENTLY BOUGHT A BOAT WITH A 1979 50HP MERCURY BLUEBAND AND THERE IS A YAMAHA TACHO IN THE CONSOL. THEY ARE NOT WIRED TOGETHER.
I HAVE A WIRING HARNESS TO PLUG INTO THE CONTROL BOX AND OFF THAT I GET A BLACK (GROUND), BROWN (REFERENCE?-WHAT DOES THAT MEAN), AND WHITE, YES WHITE (SIGNAL?) WIRE.

THE REV COUNTER HAS ONLY 2 WIRES FOR INPUT A BLACK AND A BLUE, I THINK BLACK IS GROUND AND BLUE IS SIGNAL.

BASICALLY CAN I CONNECT THE TWO TOGETHER SOMEHOW AND THE REV COUNTER WORK? READ LOADS OF THESE FORUMS AND MAINLY THERE ARE 3 INPUTS - OR 4 INCLUDING THE LIGHT TO A TACHO. NORMALLY, I DONT UNDERSTAND HOW THE 2 WIRE YAMAHA WORKS.

AFTER LOOKING FOR AGES I GOT BORED AND WIRED BLACK TO BLACK AND BROWN TO BLUE REV COUNTER WENT OFF THE SCALE WHEN KEY TURNED AND ENGINE FIRED UP., SO TRIED WHITE TO BLUE, NOTHING WHEN KEY TURNED AND ENGINE FIRED UP,

ANY IDEAS FOLKS PLEASE, CHEERS

seabob4 posted 07-24-2008 09:47 PM ET (US)     Profile for seabob4  Send Email to seabob4     
Although Mercury and Yamaha teamed-up to get Mercury through their four-cycle introduction a few years ago, 1979 was way to early for any collaboration. Sounds like the previous owner had a Yamaha on board, swapped out the motors, and didn't give a care about the tach.

You want a Tachometer that will look good and work with your motor, like Faria Euro with a 316SS bezel.

jimh posted 07-25-2008 08:31 AM ET (US)     Profile for jimh  Send Email to jimh     
For help interpreting the color codes used in marine wiring see

Marine Wiring Color Codes
http://continuouswave.com/whaler/reference/wireColorCode.html

For help understanding the electrical basis for tachometer operation, see the subheading "Tachometer Signal" in

Permanent Magnet Alternators
http://continuouswave.com/whaler/reference/PMA.html

jimh posted 07-25-2008 08:36 AM ET (US)     Profile for jimh  Send Email to jimh     
If I understand your narrative correctly, the tachometer has two input terminals and you are provided with three circuits which may be connected. There are only six permutations of interconnection possible. However, by identifying one of the inputs as the ground and one of the circuits to be connected as a ground, we can eliminate all but two of the permutations possible. With only two possible configurations, it should be straightforward to explore them experimentally and determine if either provide the desired function. Please report back with your findings.

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