Abstract: A cart, transportable along rails in the bed of a boat trailer, engages an eyelet at the bow of the boat and guides the boat into and out of the water. Uprights at the rear of the trailer maintain the boat in alignment with the trailer and the boat supporting elements thereof during transport of the boat on and off the trailer. Automatic latches are employed to interconnect the boat with the cart and the cart with the trailer and thereby permit loading and unloading of the boat by one person.