At Talbot Rink in Gloucester, a night after clinching the Catholic Central League/Large crown, the Spartans (11-2-3) needed a third period goal from James Perkins to get out of Dodge with the win.
"We really didn't come to play, and give Gloucester a lot of credit, they challenged us all game long," St. Mary's coach Mark Lee said.
The Spartans actually trailed 1-0 after one period on a goal from Gloucester's Mike Russo. St. Mary's tied the game early in the second on defenseman Nikko Markham's goal, assisted by Connor Parent.
Perkins notched the game winner at 2:52 of the third, assisted by Bucky Surette and Tommy Braswell.