going to 12v to 24v you need to run 6ga. wire to allow for the extra curent,& yes you are right about the wiring.The neg. goes to the pos.& then the remaning pos.& neg.go to the troling motor.The mounting holes will be diffrent.however you might be able to use 2 of them,the 2 in front or the 2 in back.I just switched from a 12v mg to a24v mk & was able to use 2 front holes. Took about 3 hours to run 6ga.wire & mount new motor.Hope this helps.