Battery connected backwards - quick question

[MetsFan9]

My friend is restoring his boat and he was replacing his trolling motor recepticle and cut the wires from the trolling motor to the old recepticle. Thus no power is connected to the trolling motor currently. While waiting for the new recepticle for the TM and plugs he decided to hook up his depth finder on his bow. I helped him connect the depth finder. When he hooked up the battery he connected the terminals backwards. Upon noticing this I told him to disconnect the terminals and rig +/+ and -/-. Still no power on the unit, luckily the battery that was rigged backwards was only connected to the trolling motor which was not wired yet. So the depth finder is now running off the starting battery. Question is will connecting the battery backwards cause any damage to fuse or wiring with the battery not wired to the trolling motor yet. My guess is no damage as nothing was connected to the battery. Just a question can anyone verify this.

[Mini]

if nothing was connected then nothing can be damaged. The battery doesnt know what color the wires are! Now if they were hooked up and the ends of the leads touch then you could have problems.

[dpman79]

Maybe I am not following you right here, but I think that if the batteries are wired +/+ and -/- then you are running a 12 volt system. they must be wired differently to get a 24 volt system.

[basshole45]

if it wasnt hooked up to the sonar i dont see why it would have popped a fuse,,,he may have messed the battery up ,,but im guessing since its hooked up the wires run to a breaker prob 2 40 amp breakers that switch the power from 12 to 24 volt he may have popped one and need replaced,,