An apparatus for mounting boats to a trailer by using the thrust of a motor in a boat to cooperate with an alignment mechanism to keep the bow in alignment. Similar arms with cooperating rollers mounted thereon are cammingly separated when the bow pushes against one or both of them. The reaction force is proportional to its deflection thereby helping, within certain limits, the alignment of the bow. By keeping the synchronization of the arms movement the boat's bow can be more readily aligned to facilitate the mounting of the boat to a trailer without requiring additional help. The arms carrying the rollers are resiliently biased in a predetermined position that is overcome by applying a force of a predetermined magnitude.