What was found
EXTERNAL SNAP RING ON PROPELLER BLADE CAME OFF AFTER PREFLIGHT ENGINE HAD STOPPED ON INITIAL START, THEN WAS RESTARTED. SNAP RING CAME OFF BLADE SHANK BUT WAS RETAINED BY SPINNER. THEN AIRPLANE WAS FLOWN FOR 2 HOURS WITH FIVE TOUCH AND GO LANDINGS, WITHOUT FAILURE OF PROPELLER. PROPELLER WAS THEN REMOVED AND TAKEN BACK TO OVERHAUL SHOP WHERE TEAR-DOWN WAS COMPLETED. FINDING WAS SNAP-RING WAS NOT SEATED PROPERLY. THE BLADE TO PISTON LINK WAS DAMAGED AND REPLACED. THE PROPELLER BLADE WAS DRESSED AT SHANK.