THE PLT REPORTED THAT AFTER TAKING OFF, THE GEAR WARNING HORN SOUNDED WHEN HE RETRACTED THE GEAR. HE CONTINUED EN ROUTE WHILE TRYING TO GET A SAFE INDICATION. SUBSEQUENTLY, APRX 20 MI EAST OF THE DEPARTURE POINT, HE ELECTED TO ENTEND THE GEAR & RETURN TO THE ARPT. AFTER INITIATING A TURN BACK TO THE WEST, HE HEARD A LOUD BANGING OR KNOCKING NOISE FROM THE FRONT OF THE ACFT. ABOUT 30 SEC LATER, THE ENG COMPLETELY LOST POWER. HE FOUND AN AREA OF RELATIVELY FLAT TERRAIN AMONG STEEP MOUNTAIN RIDGES & ELECT TO LAND THERE. DURING THE LANDING, THE ACFT BOUNCED & SLID TO A STOP ABOUT 100 FT FROM THE INITIAL TOUCHDOWN POINT. A SUBSEQUENT ENG TEARDOWN & METALLURGICAL EXAM REVEALED THAT THE CRANKSHAFT HAD FAILED FROM FATIGUE AT THE CHEEK JUST FORWARD OF THE #3 BEARING. THE ACFT HAD PREVIOUSLY BEEN INVOLVED IN A MISHAP ON 1/19/80, IN WHICH, THE PROPELLER WAS DAMAGED. REPORTEDLY, THE ENG HAD NO POWER & THE PROPELLER WAS WINDMILLING DURING A LANDING IMPACT ON 1/19/80.