Re: 12v or 24v
The 2 batteries would need to be hooked in series inh order to get the 24v needed. You would take the heavy guage battery wire and connect 1 positive to the negative on the other battery. You would then attach the trolling motor wire to the one positive on 1 battery and 1 negative on the other battery(The terminals that were not used in the first step).
The main reason is to get additional use out of the system prior to needing a recharge.