What happened
The pilot had been monitoring an increase in the fuel burn rate over a period of time. For best power operations from 5,800 feet mean sea level, the pilot's normal leaning procedure required increased mixture control travel. On the day of the accident, the engine had failed to respond to throttle input on two separate occasions. The loss of engine power occurred while the aircraft was flying low to the terrain.
The investigation
Post-accident examination of the carburetor revealed a black composite float that felt heavier than normal. The engine spark plugs exhibited light fuel soot. Regarding the aircraft structure, one pontoon showed light damage to the smooth shell.
An investigation into the component hardware referenced Precision Airmotive Corporation's "mandatory" Service Bulletin MSA-1. This bulletin, issued by the carburetor type certificate holder, addresses reports that composite floats may absorb fluid and sink. The bulletin directs the replacement of existing composite floats with metal floats to prevent disruptions in fuel flow. While Precision Airmotive considers this replacement mandatory, compliance remains optional for operators flying under 14 CFR Part 91.