What was found
PROPELLER INSTALLED NEW 9-11-81, FACTORY INK STAMP ON BLADE SHANK INDICATED PROPELLER HAD NEVER BEEN OVERHAULED. PROPELLER REMOVED TO REPLACE MOUNT SEAL AND OLD NUTS, USED FOR 2-HOUR FLIGHT. FOUND SOME NUTS LOOSE, INSTALLED NEW NUTS. AIRCRAFT FLOWN ADDITIONAL 60 HOURS AND REMOVED DUE TO INCREASING VIBRATION. BOTH DRIVE DOWELS FOUND BROKEN WITH SIDE WEAR ON MOUNTING STUDS. HUB FOUND CRACKED IN THREADS OF NR 1 BLADE SOCKET.