Matt Sundberg added 12 points for the Cougars, who claimed fifth place in the Battle 4 Atlantis tournament.
Field goal shooting was the difference in the game. The Cougars (5-1) shot 50.9 percent (29 of 57) from the field, including making 14 of 25 attempts in the second half. They also made 12 of 23 from 3-point range for the game.
Meanwhile, UMass shot only 34.7 percent (25 of 72) and made 4 of 28 from 3-point range.
The Cougars led 38-34 at halftime and broke the game open with a 20-4 run in the second half. A laypup by Stitt capped the run and gave Charleston a 68-47 lead with 6:50 remaining.