St. Peter's erased a nine-point deficit in the last five minutes, tying the game at 67 on Desi Washington's free throws with nine seconds left. But Hart answered with an acrobatic layup and the Peacocks' long 3-pointer at the buzzer was off the mark.
T.J. Curry had 13 points and Hart 12 for the Red Foxes (6-23, 5-14 Metro Atlantic).
Lewis scored 20 points and Marist shot 64 percent (16 of 25), including 9 of 15 from 3-point range, to take a 43-25 lead at the half.
St. Peter's, which shot 30 percent in the first half, made 16 of 30 shots in the second half.