NORTH BILLERICA – They weren’t even supposed to be in the state tournament following an ugly postgame brawl against Arlington Catholic.Yet the St. Mary’s boys hockey team now finds itself one win away from a title.The Spartans stunned top seeded Burlington with goals on their first three shots Wednesday in the Division 1 North semifinals at Chelmsford Forum and a 24-save performance from Donald Hesse en route to a 5-0 win and their first sectional final berth since 2006.In the ultimate case of irony, the Spartans will have to face AC on Saturday (7:40) in the title game. The Cougars upset No. 2 Central Catholic, 3-1, in the other semi on Wednesday.”I am extremely proud of this young team,” St. Mary’s coach Mark Lee said. “They are reaping the benefits of all their hard work they’re putting in.”Most of the crowd hadn’t even settled in their seats before St Mary’s (16-8-1) had stunned Burlington.Bobby Mullins got the Spartans off and running 97 seconds in when he took a Derek Stella pass and beat Red Devils goalie Chris Irwin with a backhander.On the very next shift, James Perkins one-timed a Tom Braswell pass from behind the net past Irwin for his first goal of the season.Before the Red Devils could even regroup, St. Mary’s had scored on its third straight shot as Brendan Mageary one-timed home a Mullins pass for a 3-0 lead just 2:37 in.”That quick start was nice but it was a product of our forecheck that forced turnovers,” Lee said.Burlington got its legs back late in the first and nearly cut into the lead but Hesse stoned Steve Mattos’ rebound chance late in the first.”In the tournament, you can only go as far as your goaltender takes you,” Lee said. “And Donald has been great for us in the postseason.”The blue and gold kept on rolling in the second as James Perkins upped the gap to 4-0 less than a minute in.Burlington would get three power play chances in the second, but failed to score as Hesse stopped all 12 shots he saw in the middle period.St. Mary’s put the game on ice midway through the third when Mike Restuccia converted on a breakaway off a Corey Bartlett pass.”Now we have an opportunity on Saturday to face an experienced AC team,” Lee said. “We’re just excited to be playing for a championship with this young team.”