The Gamecocks (5-3) had a 10-point lead with 9:18 remaining, but Winthrop (3-3) fought back into the lead on Keon Johnson's layup. Townser followed with two layups, but Johnson tied it up twice in the final minutes with a 3-pointer and two free throws to force overtime.
DJ Felder hit two free throws to give Jacksonville State a 76-75 lead in overtime. Johnson was sent to the line and made the first, but couldn't sink the go-ahead free throw with 11 seconds left, setting up Townser's game-winner. Winthrop didn't get a shot off as time expired.
Johnson led Winthrop with 22 points and Tevin Prescott had 15 with 11 boards.