Re: wires for gauges
Wiring Colors for MerCruiser
Color Code Where Used
Black All Grounds
Brown Reference Electrode-MerCathode
Orange Anode Electrode-MerCathode
Lt. Blue/White Trim- ?Up? Switch
Gray Tachometer Signal
Green/White Trim -?Down? Switch
Tan Water Temperature Sender to Gauge
Lt. Blue Oil Pressure Sender to Gauge
Pink Fuel Gauge Sender to Gauge
Brown/White Trim Sender to Trim Gauge
Purple/White Trim-?Trailer? Switch
Red Unprotected Wires from Battery
Red/Purple Protected (Fused) Wires from Battery
Red/Purple Protected (+12V) to Trim Panel
Orange Alternator Output
Purple/Yellow Ballast Bypass
Purple Ignition Switch (+12 V)
Yellow/Red Starter Switch to Starter Solenoid to Neutral Start Switch
or see this link
http://www.boatfix.com/merc/Techbk/94/94hg4d.pdf