U.S. Coast Guard 2013 Recreational Boating Statistics Table 17, version 2 (as captured 11 June 2014). This version switches the data rows for struck by boat and struck by propeller.
Houseboat Propeller Regulation Proposed and Withdrawn by USCG: Analysis by PGIC
History of Boat Propeller Safety
Mitigating Boat Propeller Injuries & Fatalities Chart
Four Volume Review of the Boating Industry’s Boat Propeller Guard Product Liability Defense