The Punahou School boys basketball team scored another breakthrough victory last night, holding off Mercer Island (Wash.), 52-41, in the semifinals of the Fifth Annual Punahou Holiday Classic.

The Buffanblu (12-2) will play Salesian (Richmond, Calif.) at 7:30 tonight for the championship. Three weeks ago, Punahou snapped four-time defending state champion Iolani's 104-game win streak against Hawai'i opponents, and last night's win was the Buffanblu's first against a Mainland team in at least three seasons.

Mercer Island (4-5) has been struggling so far this year, but traditionally is one of the most respected programs in the Northwest. The Islanders, who produced former Duke standout and Missouri coach Quin Snyder, missed the state tournament last season for the first time in 22 years.

"We had never beaten a Mainland team since I've been (on the varsity), so it feels good," said Punahou junior Spencer McLachlin, a third-year player who finished with 13 points.

Ten of McLachlin's points came in the first half, when the Buffanblu took control with a 29-13 lead. His layup with 3:50 remaining in the second period started a 15-0 run that was capped by Miah Ostrowski's two free throws with no time left.

Punahou, which often substitutes five at a time, got points from eight players in the first half.

"They're a nice team," said Mercer Island coach Ed Pepple, in his 38th year at the Islanders' helm and 48th overall. "They've got a few good big guys and a great point guard (Ostrowski), and they have good balance and variety to their game. We just started with too many turnovers and couldn't handle the ball. We're not very experienced."

Still, Buffanblu coach Greg Tacon warned his team at halftime to be wary of Mercer Island.

"I told our kids that Coach (Pepple) has more career wins than me and my two assistants — who used to be head coaches — put together, times 10," Tacon said. "He's been down by more (than 16 points) to better teams than us."

Tacon's warning proved true, as the Islanders cut the lead to 40-34 early in the fourth period. But that was as close as they would get, as Ostrowski answered with a 3-pointer from the corner and Danny Cho scored on a layup to make it 45-34.

In the final tally, Ostrowski finished with 13 points and three steals and 10 different Punahou players contributed with either points, rebounds or steals.

"Before the game, Coach told the second five that he's not putting them in just to hold the lead; he expects them to keep pushing harder and build on it," McLachlin said. "They took it to heart."

Tacon said the reserves have been playing a big role all season, and they can expect that to continue.

"Playing a lot of people lends itself to confidence," Tacon said. "Those guys know that they're going to get a chance to play, so that makes them more confident."

Kael Kristof led Mercer Island with 15 points and Trevor Fulp added 10 points, all in the fourth period.

Reach Wes Nakama at wnakama@honoluluadvertiser.com.