DeAndre Kane finished 6 for 11 from the field, adding eight assists and three blocks.
Scarver scored 10 points in the first half and went 3 for 3 from behind the arc to help Marshall build a 35-20 advantage at halftime.
Longwood improved from 22.6 percent shooting (7 of 31) to 38.5 percent (10 of 26) in the second half, but failed to cut the lead as it was outscored 46-27 in the second half.
Longwood was led by Michael Kessens' 11 points and five rebounds, while Jeylani Dublin added 10 points and grabbed eight rebounds to lead Longwood off the bench.
Niqel Spikes nearly missed a double-double for Marshall with 10 points and nine rebounds to accompany his five steals.