ON A PREVIOUS FLT, LOW POWER WAS NOTED IN THE RGT ENG, THE RGT ENG FUEL FLOW WAS 5 TO 8 GAL/HR LESS THAN THE LEFT ENG & THE RGT ENG TEMP (ITT) WAS ABT 500 DEG LESS THAN THE LEFT. A DECISION WAS MADE TO FERRY THE ACFT TO A MAINT FACILITY TO HAVE THE RGT ENG EXAMINED. THE PLT TOOK OFF ON A 5186' RWY (RWY 2C) WITH A LGT TAIL WIND IN 95 DEG TEMP, THOUGH THE ARPT HAD LONGER RWYS (7702', 8000' & 8500'). A WITNESS NOTED THE ACFT LIFTED OFF AT THE END OF THE RWY (CHARTS SHOWED THE TAKEOFF ROLL WITH NORMAL POWER SHOULD HAVE BEEN ABT 3100'). WITNESSES RPRTD THE ACFT REMAINED LOW (NEARLY HITTING A 55' LGT STANDARD) UNTIL IT ROLLED RGT & 'DROPPED LIKE A ROCK.' IMPACT OCCURRED IN A RGT WING LOW ATTITUDE ABT 2 MI FM THE DEP END OF RWY 2C. THE ACFT WAS EXTENSIVELY DMGD BY IMPACT & FIRE; NO PREIMPACT PART FAILURE WAS FND. BOTH ENGS HAD EVIDENCE OF ENG ROTATION AT THE TIME OF IMPACT. THE OPERATOR'S LEAD MECHANIC HAD RPRTD FOR DUTY ABT 3 HRS BEFORE THE ACDNT FLT, BUT HE HAD NOT BEEN INFORMED OF THE ENG PROBLEM BEFORE THE ACFT TOOK OFF.