Boahen scored six in overtime, including a pair of free throws to make it a two-possession game with four seconds left.
Boahen's jumper with 16 seconds left in regulation tied it at 82 and the Tribe's Justin Pierce missed a layup with two seconds left to force overtime.
Ottey and Jordan Blount added 14 points each for the Flames, who shot 36 of 64 (56.3 percent) from the field.
Matt Milon made 8 of 15 from 3-point range and scored a career-high 30 for William & Mary (1-2). Pierce added 25 points and 11 rebounds, and L.J. Owens scored 12 in his first career start.