If I have 2 12 volt batteries, wired in parallel (+ to +, - to -, for a total of 12 volt output to the trolling motor, not 24v) - can I use a single bank charger to charge both batteries by hooking up the charger to one of the batteries?

Thanks!

No. Each battery should be charged independently.

Gman

Yes, a single bank is used if you're in parallel as stated. You are effectively charging one "big" 12V battery. Some will say that charge times will double, but that's not necessarily so. Charge time will have a relationship to how deeply discharged the batteries are during a day's fishing. One drawback about this type system is IF a battery in the parallel connection goes bad, it becomes a "load" on the other battery and will drain it prematurely also.
Using a two bank charger without disconnecting one of the jumpers could result in the charger reading itself from the other battery and "thinking" it has charged, then cutting off.
John

Yes you can. It's not much different than charging batteries in series (24v or 36v). Diesel pickups run in the same setup. A weak battery has the same effect on any multi-battery setup.