The Hawks (11-19) trailed 32-31 at halftime, thanks to a 52-percent shooting effort (13 of 25) by the Black Bears, and didn’t grab their first lead, 38-36, until the 16:42 mark of the second half.
A layup from Kevin Estes stretched Hartford’s lead to 47-40, but Maine (15-15) scored 10 straight to pull ahead 50-47 with less than 10 minutes left.
The Hawks answered with an 8-0 run and never trailed again.
Terrance Mitchell hit a pair of free throws with 57 seconds remaining to close Maine’s deficit to 63-62, but a 3-pointer from Maciel sealed the win.
Gerald McLemore, Raheem Singleton and Mitchell scored 13 apiece for the Black Bears.
Hartford will face Boston University (19-13) on Sunday in the semifinals.