[John62]

Are you sure it is a 24v trolling motor, I don't fish but I understand trolling motors are usually 12v. First you ask about multiple 12v then you ask about multiple 24v. Not sure I understand the question. Your boat motor should be 12v. If your trolling motor is 24v then if using 12v motors you connect the positive of battery one to the positive on the trolling motor. you then connect the negative of battery one to the positive of battery two. Then connect the negative of battery two to the negative of the trolling motor. that is called Series wiring. You add them together. But do not do this with three batteries or you will have 36v. Connecting this to the boat charging system likely won't work even if you disconnect the batteries to keep them 12 v each because the charging system is not built to do this and deep cycle batteries take several hours to charge.