An unmatched boat and trailer create a safety hazard when you tow your boat. You need three measurements to ensure that your boat and trailer match perfectly. The overall length of the boat determines the total length of the trailer. The length of your boat from the stern to the bow eye determines the placement of the winch post. Stern width ensures that your boat will fit onto your trailer.
Hook the end of a tape measure on the lowest part of your boat's stern. Pull the tape measure toward the front of the boat.
Align the end of a level with the bow eye. Adjust the level to sit perpendicular with the front edge of the boat. Read the measurement where the edge of the level resting against the bow eye and the tape measure meet. Write down the measurement in a notebook.
Move the 4-foot level to the forward edge of the bow. Read the measurement where the tape measure and level intersect. Write down the measurement in your notebook.
Measure the distance across the lowest point of the boat's stern to determine the width of the trailer required to haul your boat.