As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING START FOR MAINTENANCE THE PROPELLER JERKED TO A STOP. SUBSEQUENT START ATTEMPTS SHOWED NO MOVEMENT OF PROPELLER WHILE STARTER WAS RUNNING. REMOVAL OF THE STARTER AND STARTER ADAPTER REVEALED ALL SIX BOLTS THAT ATTACH THE LARGE GEAR TO THE CRANKSHAFT HAD SHEARED ALLOWING THE LARGE GEAR TO SPIN FREELY ON THE CRANKSHAFT.