Mcgard Single O B Lock 5 16 18 F SmDesigned to lock the outboard onto the transom, simply replace one of the mounting nuts with a McGard locking nut. A free spinning collar turns if attacked by gripping tools, protecting against theft and inconvenience. (74049 fits most of the motors listed and will fit other small outboards with a 5 16" hole in the transom bracket for mounting the motor.) Description : 5 16 18 Honda 8 30 hp, Johnson Evinrude 6 30 hp, Merc Mariner 8 25 hp, Nissan 8 18