Here's my solution to getting my boat into the water while keeping my car out of the water. I unbolted the coupler from the 3 inch square trailer tongue and bought a 12 inch long standard class III receiver tube to put in its place. The ID of the tongue (2.75 inch) and the OD of the receiver tube (2.5 inch) didn't quite match, but 4, 9 inch long pieces of 2 inch wide, 1/8 inch thick steel made excellent shims. The receiver tube was secured in place by drilling and tapping holes for 16, 5/8 inch long, 3/8 inch bolts. The new coupler is bolted to a 7 foot long piece of 3/16 wall 2 inch steel tubing, which is inserted into the receiver tube. The coupler can be pinned short for towing, long for launch and retrieve and removed completely for storage.