Abstract: An anti-theft locking system for marine outboard and out-drive units is provided. This system initially locks the motor propeller to the foot of the out-drive unit, and then allows a chain or cable to be used to lock the device, the boat, and the trailer to an immovable object. The locking system utilizes a locking member with a hook that engages the propeller, and wraps around the foot of the marine drive unit, providing a lockable portion to affix the device to the propeller and foot of the marine out-drive unit.