Brunswick Corporation’s Starter Interlock, U.S. Patent 4,064,823. This safety feature is to prevent outboard motors from starting in neutral.
Houseboat Propeller Regulation Proposed and Withdrawn by USCG: Analysis by PGIC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