I had a 16 ft fiberglass driftboat that I pulled with a 4x4 Toyota with a 4 cyl. motor, the truck had oversized tires on it when I bought it and it had a hell of a time pushing them tires, the couple times I pulled the boat I was sure I was going to blow that 22R motor. My dad convinced me to dump the tires and go back to stock, the difference was pretty significant, not to mention the improved gas mileage. I had no problem doing 60-65 on the flats and 50-55 on inclines.