Mountaineers center Aaric Murray came in off the bench in the second half and finished with 10 points and five rebounds.
Henderson had all his points in the first half to help West Virginia (1-1) take a 51-19 halftime lead. The Mountaineers made 22 of 39 shots during the opening half, while Marist went 5 for 20.
West Virginia's margin of victory was the largest at the Old Spice Classic. The previous mark was set in 2010 when Texas A&M beat Iona 74-55.
Juwan Staten converted a pair of free throws midway through the second as West Virginia went up 65-26. Harris' layup made it 81-36 with four minutes to play.
Henderson had a slam dunk and then hit a 3-pointer as West Virginia took a 24-9 advantage eight minutes before intermission. Harris had a 3-point play, slam and layup to extend the Mountaineers lead to 37-14.
Humphrey finished with 10 points and teammate Jabarie Hinds had 11.
Murray played only 15 minutes Thursday after recently being late to practice.
No. 17 Gonzaga is also participating in this weekend's Old Spice Classic.