The Eagles nursed a 25-24 halftime lead before running out to a 40-33 lead at the end of the third frame to take control of the game and then put it away in the final eght minutes.
Four Eagles cracked double figures for the balanced hosts, with Jesse Kunzweiler and Dylan Spieler leading the way with 16 points each, Zach Specht adding 15, and John Hoefling 10.
Beau Pick paced the Hawks with 17 points, and Tyler Delperdang added 11.
St. Mary's made 18-43 shots for 42 percent and was 5-10 from the free throw line. The Hawks were 7-15 for three-balls.
"The game was a see-saw battle through three quarters," noted MMC coach Pat Bird. "At the four-minute mark in the third period St. Mary's took a two-point lead 31-29. We then pulled ahead by seven at the end of the quarter.
"I was really happy with the way our guys pulled away from them in the third and fourth quarters. During the Christmas break we stressed the importance of finishing games strongly. The boys worked well together and we were able to put four guys in double figures."
The MMC teams play at West Sioux in Hawarden tonight.