The Instructions for Setting a Steering Trim Tab on a Boat Motor

When your power boat won't back up straight, no matter how straight you hold the wheel or tiller, blame your propeller and Sir Isaac Newton. Your propeller turns and has sideways momentum built up before your boat begins to back up. It transfers that sideways momentum to your boat. Sir Isaac's First Law of Motion says once something begins to move, it won't change directions until something else makes it do so. That means the sideways momentum of your boat won't stop unless something -- like the motor's trim tab -- steps in to change its direction.

Instructions

    • 1

      Back your boat up in the water. While the boat is backing up, move the gear shift to neutral. Note the side to which the boat pulls as it stops.

    • 2

      When you remove your boat from the water, use a china marker to make a small mark on the motor's propeller shaft housing to indicate which side the boat pulled toward when you backed up

    • 3

      Loosen the nut that holds the trim tab on the motor with an adjustable wrench. Twist the trim tab about 20 degrees away from the side of the motor that has the mark on the propeller shaft housing. Retighten the nut.

    • 4

      Back the boat up in the water and move the gear shift to neutral once more, when you next go boating. If the boat still pulls to one side, repeat the process of loosening and resetting the motor's trim tab until the boat backs up straight.