As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED LOSING RT ENGINE MAP AT 9000 FEET AND NOTICED OIL LEAKING FROM RT ENGINE COWL. THE RT PROP WAS FEATHERED AND RT ENGINE SHUTDOWN AND THE ACFT RETURNED TO DEPARTURE AIRFIELD. MX INSPECTED AND FOUND THE CRANKSHAFT GEAR WAS SEPARATED FROM THE CRANKSHAFT. A REPLACEMENT ENGINE WAS INSTALLED. THE ORIGINAL ENGINE WAS SENT FOR DISASSEMBLE AND EVALUATION. THE ENGINE FACILITY VERIFIED FAILURE OF THE CRANKSHAFT BOLTS.