Inspection authorized technician reported finding the throttle arm rod end bolt missing after a power loss during flight. They previously installed the hardware in accordance with the Cessna 150 Illustrated Parts Catalog.

Narrative

Aircraft suffered power loss during flight. Aircraft made successful and safe off airport landing. No aircraft damage. No property damage. Upon maintenance inspection; found the throttle bolt missing. I was the primary mechanic on engine installation. The aircraft parts manual was used to determine correct hardware for the throttle arm to rod end. Per the IPC (Illustrated Parts Catalog) this hardware was used. Which was AN3 bolt and lock nut. Its is unknown why this bolt/nut combination went missing. After further review after the incident; Cessna Customer Care Advisory letter SE79-6A was located. Dated 4/13/1979. This advisory recommended replacing the lock nut with a castle nut and cotter pin. This letter will be accomplished now on this aircraft. This letter was not mandatory. Cause: Unable to determine actual cause. All new aircraft do incorporate a castle nut on engine controls; Prior to 1979; this was not mandated.The current Cessna 150 IPC still calls for a lock nut/un drilled bolt combinationSuggestions: Change the current IPC to reflect the recommended bolt/nut combination