Three wires are generally used. Run 12V to the Ignition post from your ignition switch. Run ground to ground. Run purple wire in the wiring harness to the "signal" or "tach" terminal. My book kept talking about the white "tach" wire but it was wrong. The wires were properly marked at the terminal strip on the engine. If you want to light the gauges you can either jump from the ignition to the light so the light will always be on or you can run 12V from the "lights" switch of your boat to the light terminal so you can turn the gauge light on and off seperately.
Look for a purple wire under the instrument panel that isn't attached to anything. (Verify that the wire attached to the junction block under the motor cowl is in fact purple, though.)So am I to assume that there is already a harness there? My panel only has a speedo, as seen here..
The wiring harness we're talking about is whereever your key is. That switch generally has all the wires from the outboard sent to it. There will likely be a purple and orange wire not attached to anything coming up the harness from the engine. The purple one will be for the tach signal. The orange one is for the overtemp buzzer. If you don't have the buzzer, I highly recommend you add it.
Marty
http://www.martyhammersmith.com
Beckspop,
Here is a close up pic of my Capri console showing the Nav aids that seem to have been sun-bleached out of your graphics.
The dentist in your town, Michael, and I were in the same car show a few years back.
Al