I have a Sears 1970 12 foot jon boat. My son and I just finished setting it up. I have bought a Minn Kota 50lb thrust trolling motor to get us around on the lake. The batter weighs a ton in its box and if I set it in the rear ahead the transom and then I weighing 245lb set in back With this make the boat sink to point it takes on water. My son will be riding in front but weighs only 84 pounds. Will it be too much weight in rear to hurt boat functioning? thank you guys.