I finally have a duplicate title for both trailer and boat and am getting both ready to list for sale. I need to replace the winch on the trailer (galvanized, but except for the hardware, which is fine, everything rusted.) How high a weight capacity do I need to pull in an M15? Is it enough to exceed the weight of the boat or should there be some margin of safety and if so, how much? Bobbie M15 LiftOff