Eric Washington added 11 for the Blue Hose, who shot 53.3 percent (23 of 43) and snapped a two-game losing streak.
Presbyterian scored the first five points and led by as many as 11 before taking a 35-28 lead into the break. Winthrop cut the deficit to one, 42-41, in the second half but McTavish, who had eight points on 3-of-3 shooting, answered with a 3-pointer that sparked a 12-4 run for the Blue Hose.
Winthrop matched Presbyterian’s hot-shooting with a 53.5-percent (23 of 43) clip but made just three treys, compared to nine for the Blue Hose.
Presbyterian matched a season-low with 21 rebounds but held Winthrop to just 19 boards.
Joab Jerome led Winthrop with 20 points and Derrick Henry added 12.