BLUE HILL — The No. 1 George Stevens Academy baseball team shut out the only team it has lost to all season — No. 4 Mattanawcook — on Saturday to advance to the Class C Northern Maine championship.The 17-1 GSA Eagles beat the 12-6 Mattanawcook Lynx 3-0 in the semifinals. They will play No. 2 Houlton (18-0) in the regional championship at 6:30 p.m. on Tuesday at Mansfield Stadium in Bangor.Will Entwisle doubled and singled for the Eagles while Taylor Schildroth chipped in a single and an RBI.For Mattanawcook, Jordan Hanscom and Brady Pepin each had two singles.This is placeholder textThis is placeholder textThough the Bucksport Golden Bucks beat GSA in last year’s regional championship, they wouldn’t have the opportunity to defend their title.No. 6 Bucksport (8-11) lost to Houlton 5-4 in Saturday’s Class C North semifinal game in Houlton. Zack Hagan hit an RBI-single in the bottom of the eighth to lead Houlton to the walk-off victory.Bucksport jumped out to a 2-0 lead. But, in the fifth inning, Colby Callnan sparked a rally with a pinch-hit RBI-single. Billy Phillips earned the win in 1 2/3 innings of hitless relief for Houlton.For Bucksport, Andy Allan had two hits, and pitcher Matt Vincent struck out five while giving up four hits.Before ending their season, the Golden Bucks managed to knock off No. 3 Central 7-3 in Thursday’s Class C North quarterfinal.Tanner Stegner had three hits and scored three runs to pace Bucksport. Matt Vincent added two hits and scored twice. Jacob Gauvin pitched five solid innings on the mound, and Vincent came on and pitched the final two.Andrew Speed led Central (9-8) with two hits, including a double, an RBI and a run scored. Zach Randall pitched into the seventh for Central before miscues helped Bucksport extend its 4-2 lead.