A BE58 ACR PLT REJECTS 2 TKOFS IN A ROW WHEN THE R ENG LOSES PWR DURING THE TKOF ROLL. AFTER THE ENG IS COOLED A FULL PWR CHK AND TKOF IS SUCCESSFULLY MADE; HOWEVER; THE ENG HAS MINOR FLUCTUATIONS DURING CRUISE.

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AFTER DROPPING OFF OUR PAX; WE WERE ATTEMPTING A TKOF ON RWY 3 AT DCA. ALL COCKPIT INDICATIONS WERE NORMAL UP TO THAT POINT. DURING THE TKOF ROLL; WE EXPERIENCED AN ABRUPT LOSS OF PWR FROM THE R ENG. THE TKOF WAS ABORTED SAFELY AND WE TAXIED BACK TO RWY 3 FOR A SECOND ATTEMPT. THE SECOND ATTEMPT PRODUCED THE SAME PWR LOSS AND RESULTED IN A SECOND ABORTED TKOF. WE THEN TAXIED BACK TO FBO AND LET THE ENGS COOL DOWN FOR 1 HR. UPON RESTART; ALL COCKPIT INDICATIONS WERE NORMAL. I SUSPECTED VAPOR LOCK AS A POSSIBLE CAUSE OF THE PWR LOSS AND DID A RESTART ACCORDING TO THE CHKLIST IN THE AFM USING THE BOOST PUMPS TO TRY TO PURGE THE SYS. WE ASKED FOR A TAXI TO A LOCATION PERMITTING A FULL PWR RUNUP. I CONDUCTED 2 FULL PWR RUNUPS; BOTH WITH AND WITHOUT THE BOOST PUMPS. ALL COCKPIT INDICATIONS WERE NORMAL AND THE ENGS CAME UP TO FULL PWR; SMOOTHLY AND EVENLY. A THIRD TKOF WAS ATTEMPTED ON RWY 33. THE TKOF AND CLB WERE NORMAL. INFLT; I NOTICED MINOR FLUCTUATIONS IN THE R FUEL FLOW GAUGE AND HEARD A SLIGHT CHANGE IN PITCH FROM THE R ENG INTERMITTENTLY. NO NOTICEABLE CHANGE IN RPM WAS OBSERVED DURING THE PITCH CHANGES. UPON LNDG AT HVN; THE SIT WAS RPTED TO THE CHIEF PLT; MAINT PERSONNEL; AND DISPATCH.