An invertible, boat outboard motor lock that places an impenetrable enclosure around the pivotable arms of a pair of cap screws that are used to frictionally affix a boat motor to the transom of a boat. When in place and locked, access to remove the boat motor from the boat is blocked. The pivotable arms are placed into either end of a trough formed in a unitary block and the assembly is placed into a concave cover housing. The housing may be installed in either of two orientations, 180 degrees apart. A lock cylinder is passed through the housing and block preventing their separation.