What happened
Less than one hour into the flight, the engine began operating with a rough condition. In an attempt to rectify the issue, the pilot attempted to apply carburetor heat by pulling the control lever. However, upon pulling the lever, the inner cable of the assembly pulled out completely, rendering the pilot unable to apply heat to the carburetor.
As the engine power continued to deteriorate, the pilot elected to return to the departure point. The aircraft was unable to maintain its altitude and, while less than one mile from the shore, the pilot was forced to perform a ditching approximately 1500 feet from the shoreline.
The investigation
An examination of the carburetor heat cable assembly revealed that the inner movable cable had been worn to a point. The failure occurred approximately eighteen inches from the attachment point on the carburetor. The pilot noted that the worn section of the inner cable was located at a bend within the cable assembly. Additionally, a review of weather data indicated that atmospheric conditions were favorable for the formation of carburetor ice.