So far so good - was looking for something to get the thieves to move on the next boat and stay away from mine - I don't know what type of tool it would take to get this off without the lock but it would not be easy.  Also bought the MCGard 74036 Outboard Motor Lock Set to go with it also.  So far so good - don't know how a thief would ever get the prop off my boat without the key.