Brian....I'm going through the same problem.....I have a plug that I used on my other boat and it has 8 guage wire coming out of it.

I planned on using it but couldn't bring myself to solder 6 guage wire to the 8 guage behind the plug...

Mine is a 12 volt 54lb and it has 8ga. coming out of the trolling motor so I know the 6 is overkill....

Does yours have 6ga or 8????

Here's the wiring diagram for the 12/24 system from motorguide...

http://www.motorguide.com/index.pl/12_volt_and_24_volt

......What kinda boat are you installing it on????....Warren