The win snapped a four-game Maine (16-8, 8-3) losing streak to the hosts and evened the all-time series at 8-all. UMBC had defeated the Black Bears, 56-55, nine days ago in Orono.
McLemore broke the game open in the second half, hitting 13 consecutive Black Bear points, as Maine increased a 51-34 lead at the 12:05 mark to 64-36 with 8:38 remaining. He was the visitors' America East Player of the Game.
Senior wing Matt Spadafora, the Retrievers' America East Player of the Game, led UMBC (2-22, 1-10) with 14 points, but the Retrievers were outrebounded, 47-20. Maine scored 19 second-chance points to three for the hosts.
UMBC scored the game's first four points, but Maine went on a on 12-0 run to take command with a 12-4 advantage at the 15:41 mark. The Black Bears hit 10 of their first 18 shots from the floor and McLemore hit four of five behind the arc and the visitors led by as many as 15 points on three occasions in the first half before settling for a 34-21 halftime lead.
Conversely, UMBC misfired on 19 of 28 shots and all nine shots from three-point range in the first 20 minutes.
Maine junior post Sean McNally added 12 points in a balanced Black Bear attack. The visitors his 19 of 31 shots (61.3%) in the second half and topped the 50 percent plateau (32 of 60, 53.3%).
The Retrievers travel to Hartford to take on the Hawks on Thursday.