DRG THE TAKEOFF ROLL, LGT COLORED SMOKE WAS SEEN TRAILING THE THE ACFT. THE PLT RPRTD THAT AT 100 TO 200 FT AGL, THE ENGLOST PARTIAL PWR. HE SAID HE CHECKED ALL CTLS & RAISED THE LNDG GEAR. WITNESSES RPRTD THAT AT ABOUT THAT TIME, HEAVY SMOKE BGN TRAILING THE ACFT & THE ENG BACKFIRED & QUIT. THE PLT SAID THE SAFETY PLT THEN TOOK CTL & ATMTD TO RETURN TO THE ARPT. AT ABOUT THAT TIME, THE ACFT STALLED, DSCNDD OUT OF CTL & CRASHED AT THE EDGE OF A LAKE. RSN FOR THE INITIAL PWR LOSS WAS NOT DETERMINED. THE ELEC BOOST PUMP WAS FND IN THE HI PSN AFTER THE ACDNT. THE FLT MANUAL WARNED THAT THE HI BOOST PUMP MUST NOT BE USED UNLESS THE ENG DRIVEN FUEL PUMP HAD FAILED; OTHERWISE, INCREASED PRESSURE FM THE HI BOOSTPUMP WOULD RESULT IN ENG ROUGHNESS; IN SOME CASES, ENG COMBUSTION MAY CEASE. THE ENG OPERATED NORMALLY IN A TEST CELL AFTER THE ACDNT. WHEN ANOTHER ENG WAS TESTED, LOSS OF PWR OCCURRED 3 TO 5 SEC AFTER THE HI BOOST PUMP WAS ACTIVATED. ALSO, A CRACK WAS FND IN THE TURBOCHARGER INLET PIPE, BUT DUPLICATION OF THIS RESULTED IN ONLY A MINOR PWR LOSS.