Depending on the year of manufacture, some 70's and early 80's vintage boats had a different wiring color scheme than what has become standard today. Listed below is the comparison color code charts.
If considering re-wiring an older unit; it is best to update all the wiring colors and not to mix the two codes.

Direct Current (DC) Systems (under 50 volts)

Old Color   New (BIA) Color               Where Used

Black         Black                          All Grounds

                 Black/Yellow            Ignition kill circuit

Black         Brown                     Alternator charge light
                                                 Pumps (bilge, live-well, etc.)
                                                 Reference Electrode - MerCathode

                 Brown/Orange         Power feed to Auto-bilge switches

Black         Orange                    Accessory common feed 
                                                 Distribution Panel to Accessory switch
                                                 Anode Electrode - MerCathode

Red/White    Orange                 Alternator Output to Ammeter

Blue         Lt. Blue/White              Trim -"Up" Switch

Brown          Gray                        Tachometer Signal

                     Dark Gray               Navigation Lights

Green        Green/White               Trim -"Down" Switch

Green            Tan                         Water Temp. Sender to Gauge

Orange        Lt. Blue                     Oil Pressure Sender (10 Gauge)

Pink             Pink                          Fuel Gauge Sender to Gauge

Purple        Brown/White              Trim Sender to Trim Gauge

Purple        Purple/White               Trim -"Trailer" Switch

Red           Red                          Unprotected Wires from Battery

Red           Red/Purple                Protected (Fused) Wires from Battery
                                                  Protected (+12V) to Trim Panel

Tan           Purple/Yellow            Ballast Bypass

White         Purple                     (+12V) Ignition power feed from Switch 
                                                 Instrument power feed

Yellow        Yellow                   Bilge blowers
                                                Alternator field to reg. field terminal
                                                Starter Solenoid to Starter Motor
                                                  (MCM 470 and some Ford products)

Yellow        Yellow/Red            Starter Switch to Starter Solenoid
                                                  to Neutral Start switch

                  Tan/blue                 Warning system sense wire
                                                   (Audio warning)
               
                  Yellow/Black          Neutral Safety switch
                                                   (transmission mounted)
                 
                 White/Green            Ignition module to Distributor
                                                 (Mercury Thunderbolt ignition)

                  White/Red              Ignition module to Distributor
                                                  (Mercury Thunderbolt Ignition) 

                  Dark Green            Bonding Wires (earth ground)

                  Dark blue               Cabin, courtesy, and instrument lights

   With the addition of electronic fuel injection and other modern engine control systems, color codes and wiring systems are getting more complicated. Be very careful when testing wires for power and/or continuity. Use the chart above as reference only.