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Here is how the switch is wired on an OMC...

C = Choke or Primer
S = Start
M = Magneto
A = Accessory
M = Magneto
B = Battery

Those 6 connections correlate with the wiring diagram I gave above in a link for the wiring harness and the key switch.
There are 8 wires in the older Red Plug style wiring harness. The other 2 are for Tach = Gray wire and Tan = Warning Horn...