I agree with Dink above Looking at the photo that has nothing to do with the battery, it looks more like a loose connection, (wire in the terminal) as that's where the heat is shown. Things to check, make sure the terminal is the correct size and length for the amps of your trolling motor,make sure the terminal is crimped good . If you have a breaker or a fuse installed and its sized correctly it would have tripped the breaker or blew the fuse if the there was a short or if the wire is two small it would have melted before it would have tripped the breaker or blew the fuse. You need to cut the end off the wire and inspect if there is any sign of heat it needs to be cut out or the wire replace or your problem will still exist.