Sterett, a substitute driver for his father, Bill, Sr. in the Seattle-based Pride, scored a 1,200-point sweep and stopped Muncey's 1972 string at four straight victories.
Sterett and Muncey were tied with 800 points apiece going into the final heat on the muddy and wind-chopped Potomac River.
The two drivers battled side by side for five laps. Coming out of the first turn on lap six, the boats ran into traffic - Bob Gilliam in the Pizza Pete was just starting lap five. Sterett swung wide in the Pride and zipped pass Gilliam with no trouble. Muncey was caught behind Gilliam and had to let off and move around the Pete. The lapse allowed Sterett to open a three-second lead he carried to the finish line.
"There's no doubt who my driver is from now on," Dave Heerensperger, owner of the Pride, said. Heerensperger earlier had indicated that Bill Sterett, Sr., would drive in West Coast races.
The unlimiteds are en route to Pasco for the Tri-Cities' Atomic Cup July 23.
Muncey, driver of the Atlas Van Lines, was the odds-on favorite going into the seven-boat race after winning the Miami, Owensboro, Detroit (Gold Cup) and Madison regattas.
The Atlas still leads the national points chase with 5,800. The Pride has 4,925. The Budweiser, which placed third here yesterday, is third with 3,379. Gilliam's Pizza Pete ranks fourth with 3,016.