McGard outboard motor locks are designed to lock the bolt that holds the outboard onto the transom of the boat. Simply replace one of the mounting nuts with a McGard locking nut. A free-spinning collar turns if attacked by gripping tools. The best protection against costly outboard motor theft. Desgined for: Mercury/ Mariner 40hp and larger (2 strokes); Mercury 25hp and larger (4 strokes); Suzuki 150-300hp ; The black rubber cap is not included in McGard's outboard motor locks.;