Stillman Mahan says his role for the Portland boys’ basketball team is to be a shooter.

Mahan made the biggest shot of his life Friday night, and the Bulldogs are moving onto the Class AA North semifinals.

Mahan, who gave Portland its first lead with a long 3-pointer just before the end of the third quarter, hit a long 3-pointer before time expired to give the fifth-seeded Bulldogs a 51-50 victory at fourth-seeded Deering.

Mahan’s shot moves Portland into the semifinals against top-ranked Bangor on Tuesday at Cross Insurance Arena.

“This is big,” said Mahan. “It’s Deering, they’re our rival, our first playoff game. We’re not the best team this year standings-wise, but this win means a lot.”

Portland (11-8) went up by as many as six points in the fourth quarter, but Deering responded and when Ben Onek made two free throws with 1:27 left, the Rams had a 48-46 lead.

Lewis Gaddas tied it with a layup, but with 50.6 seconds to go, Darryl Germain got a leaner in the lane to bounce home and Deering was on the brink of advancing.

But the Bulldogs ran down the clock, Jeremiah Alado got the ball way up top to Mahan, who made the shot of his life.

“I was just trying to get open,” said Mahan. “The play wasn’t meant for me. The ball just came to me and I let it fly. They have me on the team for my shooting and I believe in my shot.”

Mahan finished with a team-high 12 points.

“I’ve been doing this a long time and I just told the guys we’ve won our share of championships, but this game ranks right up there,” said Portland Coach Joe Russo. “We had confidence in Stilly.”

“(Portland) hit a great shot and that happens,” said Rams Coach Todd Wing. “We took away their main threat and broke down their play, but their kid hit the shot. The guys played well, but there are certain things you can’t overcome.”

Just as he did in Deering’s 24-point win over Portland last week, Germain got the Rams started by draining a couple long 3s and scoring nine points in a first quarter that ended with Deering in front, 16-7.

Onek picked up two quick fouls, but the Rams forced eight turnovers.

When Germain made two free throws with 5:04 left in the half, Deering had a 24-10 advantage, but Portland roared back, thanks in part to two 3-pointers from reserve Ronaldo Wakati. A 13-0 run pulled the Bulldogs within a single point, but Loki Anda banked home a 3 to put the Rams in front at halftime, 29-24.

Deering threatened to pull away again in the third quarter as Germain’s layup gave it a 36-29 lead, but Portland went on a 10-1 run and it took a 39-37 lead heading into the fourth quarter.

Deering (12-7) got a game-high 21 points from Germain and 10 from Max Morrione. Onek had just three due to foul difficulties.