McGard Outboard Motor Lock For Mercury 1/2 20 Thread Size. 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. Features of McGard 74036 Outboard Motor Lock For Mercury 1/2 20 Thread Size Best protection available against costly outboard motor theft 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 Fully machined from high quality stainless steel and are through-hardened See long description for compatibility Thread Size: 1/2-20; Hex Size: 5/8; Overall Length: 0.750 Package Contents: McGard 74036 Outboard Motor Lock For Mercury 1/2 20 Thread Size McGard 74036: Outboard Motor Lock For Mercury 1/2 20 Thread Size