idn713,
My boat was wired like yours and when I switched to a 24 volt system I had to change a few things. The boat war wire for batteries in parrallel (12 volts) to the motor. This wiring was done through the male side of the plug. I had a toought time figuring it out like you so I opened the plug to find junpers installed between the wires from the batteries making it in parrellel. I figured out which wires needed to be powered for 24 volt set up and changed the jumper configuration. I confirmed this with my volt meter before sending power to the motor and frying something.
I hope this helps.