After speaking with a friend, the boat is probably wired for a 12/24 setup, but since my trolling motor is 24 volt only, the other red cable is not used. That would explain the extra cable. But I still have the issue of the trolling motor stuck in high speed only, even when I try turning the handle to other speeds.
Is it possible that it has to be in the water to work properly with the different speeds? Seems like a stupid question...lol. Just trying to think of possible issues.
My friend also said it might be the resistors on the circuit board, but that's beyond my abilities