Normally, the width and length of the boat determines the width and length of the trailer.
Trailers have rollers or wooden bunks to support the bottom of the boat.
Grease the bearings in the hubs of the axles to prevent bearings from seizing. Check out the trailer manufacturer s load capacity. It is very important to have proper lighting on trailers, including turn signals, and tail and brake lights. Contact the agency in your county in charge of vehicle registration for the legal requirements for lighting on trailers and trailer brake requirements. Also check the owner s manual of your towing vehicle to make sure that your vehicle is rated to tow the combined weight of your boat, motor and trailer.