About 18 minutes after takeoff, the pilot radioed that the No. 2 engine had lost power and that he was returning to land at McAllen, TX. While approaching to land, the aircraft crashed in an open field about 400 yards short of the runway and 115 feet right of the approach lights. During impact, the aircraft was in an inverted attitude, in about a 150 degree right roll and 15 degrees nose down. After impact, an intense fire erupted. An examination of the wreckage revealed no preimpact malfunction or failure except that the right propeller blades were set at 65 degrees. The angle of the blades should have been 86 degrees when in the full feathered position. The aircraft was estimated to be 753 lbs over its maximum gross weight limit at the time of the accident. With the gear down and flaps up, the Vmc was calculated to be 92 mph with the propeller windmilling and 87 mph with the propeller feathered.