As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PRE-FLIGHT INSPECTION PROPELLER WAS ROTATED BACKWARDS BY HAND TO CHECK COMPRESSION OF CYLINDERS. PROPELLER PHYSICALLY STOPPED BY SOMETHING INTERNAL IN ENGINE. AFTER INSPECTION BY REMOVING THE STARTER ADAPTER ASSEMBLY, THE CRANKSHAFT GEAR WAS FOUND TO BE MISSING ONE TOOTH FROM THE GEAR.