OMC 1984 3.8L tachometer wiring

[dlogvine]

Tachometer on the 1984 Mercedes (Freedom boat) boat with 3.8L OMC sterndrive is going all the way down to max as soon as I turn the ignition key into on position. I thought about testing the wiring first, since it could be a problem with the short circuit somewhere. However I cannot find any wiring diagram for the gauges and the wiring itself is REALLY messed up, bunch of wires twisted, bundled and fused in some places. I wondered if I can get a wiring diagram and some advice as to how to test the tachometer before buying a replacement. Thank you.
Also, I noticed that wiring of the ignition lock is done in such a way that all the accessories - bilge pump, blower, horn, lights and even trailer tilt could be used without the key in the ignition. On my Bayliner they dont work unless ignition key is turned into On position.

 

[Scott Danforth]

you want the accessories to run without the key

tach wiring is simple. red +12, black gnd, grey negative side of coil

boat gauge wiring is simple - its a standard

 

[Bondo]

boat gauge wiring is simple - its a standard

Ayuh,.... 'n I believe there's still diagrams at the top of the electrical forum,....