What was found
(CAN) PROPELLER FAILED TO GOVERN RPM IN FLIGHT. UPON ADVANCEMENT OF POWER FOR ASSOCIATED ENGINE FCU HAD TO LIMIT ENGINE RPM VIA FUEL TOPPING GOVERNOR. MAINTENANCE CREW REPLACED GOVERNOR VALVE OF PROPELLER AND COMPLETED A PITCH LOCK CHECK AND DETERMINED PROPELLER TO BE SERVICEABLE. PROPELLER FAILED TO GOVERN RPM IN FLIGHT. UPON ADVANCEMENT OF POWER FOR ASSOCIATED ENGINE. FCU WENT TO FUEL TOPPING AGAIN. ACFT WAS RETURNED FOR ENTIRE PROPELLER ASSEMBLY REPLACEMENT. PROPELLER REGULATOR ASSEMBLY SENT FOR O/H.