If that is your boat in the pic, the Ranger will be wired with 6ga and have 4 wires going to the front. The 4 wires in the front represent each of the 4 battery studs (two batteries). The 24V jump in your case is made in the plug. there is no need to double wires, but you do have a couple of options. The first being leave it like it is and connect to the same terminals in the plug that is carrying the 24V not (will be the two that is not connected to the jumper strip). this gives you a 40' jumper and will cause a small (usually not enough to worry about) voltage drop. What it does do it makes you use and extra 60A breaker since both positives going to the front need protection. The other is to disconnect the positive on battery one and negative on battery two, then disconnect the same wire in the front. Wire the 24V into the remaining pair, then place a 6ga jumper from battery 1 positive to battery 2 neg with one breaker in the positive wire going to the front. Either way will work for you.