Sounds as though the axle needs to be moved to re-distribute the weight. Sounds like a lot of tongue weight to me. You should also have a full tank of gas in the boat so it doesn't slosh back and forth. Often the width of the wheelbase can be a factor but it shouldn't be with that truck. I had to get an Expedition rather than the Explorer because of that issue. I also had to have the axle on my trailer moved a couple times before the weight of the boat was right. Prior to that it was like going down the road and having the tail wag the dog as the front wheels of the Explorer were nearly off the ground.