tach wiring

[old islander]

I have a 1978 searay 197 with an 898 5.0. My tach is not working, so I looked up under the dash and...no wires connected to it...that would explain it I guess. Anyone have a tach wiring diagram so I can get this thing working?

 

[Steverino74]

Are there any wires hanging loose? I'll bet there is? See if you can follow one wire to the rectifier module. It should connect to one of the wires from the stator at the rectifier. At least that's the way it is on my boat which is an 87 Force 125.

 

[Silvertip]

No diagram needed. Look carefully at the back of the Tach. You will see several terminals labeled "I", "S", ground and probably "L".
"I" gets connected to the "I" terminal on any other gauge. This is the terminal that gets +12 volts when the key is in the run position.
"L" gets connected to the "L" (internal light) terminal on any other gauge. This terminal gets +12 volts when the NAV/ANC switch is in the NAV position.
"G" or ground symbol. This terminal just like the others, gets connected to the ground terminal on any other gauge.
"S". This is the "send" terminal on the tach which receives pulses from the Ignition system on the engine. You need to determine which wire in the harness running from the engine to the console carries this signal. You then need to verify that the calibration selector on the back of the tach is set for your 8-cylinder engine.

 

[Blue Mist 97]

If this is a Mercruiser, your tach wire colors should be:

"I" - ignition is usually a purple wire.
"S" - tach wire is usually a gray.wire.
"L" - is usually a med. blue
"G" is black.

 

[old islander]

Ok, I think I got it. So on my Mercruiser the S wire would go to the negative side of the coil? does that sound correct?

 

[Blue Mist 97]

I believe that would be correct and should be the gray wire. You may want to check the wire with a volt meter before you hook it up, to make sure it's good

 

[Blueghost924]

The "S" connection is the "sender" connection - which should be grey. The black ground would be connected to the "G" connection. Silvertip and Blue Mist gives your the typical Mercruiser wire color code in the posts above.