ON 10/31/88, THE PLT OBTAINED WX INFO & FILED AN IFR FLT PLAN FM VERO BEACH, FL, TO HUNTSVILLE, AL. AT APRX 1513 EST, HECTCD ATC & RPRTD CLIMBING THRU 1500' FOR 3000'. ABOUT 2.4 HRS LATER, HE RPRTD A LOSS OF ENG PWR. VECTORS WERE PROVIDED TOWARD AN ARPT, BUT RADAR CTC WAS LOST ABT 13 MI SOUTH OF ALEXANDER CITY, AL. ON 11/16/90, THE ACFT WAS FND WHERE IT HADSANK IN 65' OF WATER IN MARTIN LAKE. NO PREIMPACT PART FAILURE OR MALFUNCTION WAS FOUND THAT WOULD HAVE RESULTED IN THE ACDNT. THE ENG WAS CHECKED ON A TEST STAND & IT OPERATED WITH THE ORIGINAL ACCESSORIES INSTALLED. PSNL AT THE DEP ARPT INDCD THE ACFT WOULD NORMALLY HAVE BEEN SVCD WITH THE NORMAL RAMP CAPACITY OF 50 GAL OF FUEL. FUEL CONSUMPTION WAS ESTD TO HAVE BEEN ABOUT 10.5 GAL/HR; HOWEVER, REFUELING RECORDS DID NOT VERIFY WHEN THE ACFT WAS LAST REFUELED. ALSO, THE WX COND WAS RPRTD TO HAVE BEEN CONDUCIVE TO CARB ICING.