I would think a big old barge like that would need a 12v 55 lb. thrust model at the very least. Are you using it on an electric-only lake? If electric-only I'd personally go for a 24v system and get like an 80 or 105 lb. thrust model since tht will be your sole source of power. But if using a gas motor for most of your long distance moving then you should be fine with a 55.