Abstract: An apparatus for centering a boat on a boat trailer having a chassis. The apparatus has an outrigger arm, extending upward to contact the side of the boat. The outrigger arm is movable to a position away from the boat. The apparatus also has a contact member for contacting the bottom of the boat, the contact member being movable between an upper position and a lower position. The outrigger arms and the contact member are connected together by means of an elongated bar. The elongated bar is pivotally connected to the chassis of the boat trailer. When the boat trailer is first placed into the water, the outrigger arms are in a position wide apart, and the contact members are in their upward position. The boat is then maneuvered between the outrigger arms to a position over the boat trailer. The hull of the boat contacts the contact members, forcing the contact members downward and pivoting the outrigger arms inwardly.