The best protection available against costly outboard motor theft. 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. These outboard motor locks are fully machined from high quality stainless steel and are through-hardened. A free-spinning collar turns if attacked by gripping tools. Fits the following outboard motors: Mercury/Mariner 40 hp and larger (2 stroke), Mercury 25 hp and larger (4 stroke), Suzuki 150-300 hp.