Merc 40 blue band wiring

[Rayzor]

I just removed a failed 1973 merc 500 off my starcraft. The control wiring has a 7 solid color code harness. The newer motor has a 8 color harness some with stripes and so forth. Can someone help me wire in this 40hp please. I have not been able to determin its age or find a matching schematic. Its serial number is 5559193 and its a 2 stroke 2 cyl. Thanks for ANY help.
update.... I found a schematic that nearly matches my plug and hrrness color coding. of all things its under the 70 horse (5579017) Can this be modified to work with the early (73) external style wiring?

 

[Chris1956]

It is hard to help without some additional info on your motor. The "standard" wire colors were solid, and were for the following functions. You need to trace them to make sure your motor is the same.

red: battery +
Black: ground (battery -)
Grey: choke solenoid
Yellow: starter solenoid
White: ignition power, when key is on
Brown: Tachometer signal
Orange or salmon: ign killer wire for certain ignitions, unused on others.

The new wire colors, in the same order are:

red: battery +
Black: ground (battery -)
yellow/black: choke solenoid
Yellow/red: Starter Solenoid
Purple: Ignition power when key is on
grey: Tachometer signal
black/yellow: ignition Killer wire for certain ignitions, unused on others.

Not sure what the extra wire is for. It depends on the year and model the wiring harness was intended for.

Some candidates:
Purple/red is for fused battery +
Brown is for overheat signal.
Brown/white is for temp gauge.

 

[Rayzor]

Here is the best I can describe the harness connections in the 40hp.
Yellow-blk is Choke solenoid
Yellow-red start solenoid
Red Rectifier
red starter solenoid
black=ground
Gray -rectifier
Black-yellow goes to bussbar connection turns brown and end at Merc switch? Looks similar to condenser of sort.

The external portion of the harness has a purple wire that I assume turns into battery +. Thanks for any help. Im lost.

 

[Chris1956]

The mercury switch does look like a condenser. It is supposed to ground the ign, when the motor hits something and kicks up. Connecting the black/yellow wire to this makes sense.

The grey wire should come from one of the AC posts on the rectifier. It provides a signal to power the tachometer.

Purple is likely ign power from the key switch.

The rest sounds OK.