Abstract: A case and lock for reducing damage and deterring theft of boat propellers. The invention is comprised of a case for enclosing a boat propeller and a portion of a propeller drive unit. The case has a pair of pivotally connected members which are supported by a horizontal stabilizer fin of a propeller drive unit. The lock lockably connects the case members. One optional feature of the invention are running lights mounted on the sides of the lockable case members. Another optional feature is an electronic alarm which is activated during attempts to steal the propeller.