Sunset — made up of players from Holtville and Calexico — took a three-run lead in the second inning.
Adrian Sanchez, who reached first on an error, stole second, third and home for the first run.
Eric Strahm walked and stole second and third and Eric Vargas walked and stole second. They were driven in by Ruben Sigala's single to put Sunset up 3-0.
Vargas scored again in the third. After walking and stealing second, he advanced to third on a ground out. He scored on a wild pitch to put Sunset up 4-0.
Vargas rounded the bases again in the fifth inning. After being hit by a J.R. Antuñez pitch, he again stole second and third and was driven in by a Hector Sanchez single to push the advantage to 5-0.
Imperial scored in the fifth when Antuñez doubled and advanced to third on a fly out.
Michael Bohannan drove in Antuñez on a ground out for the score. Imperial added one more run to cut the lead to 5-2.
Sunset's final runs came in the seventh when Hector Murilla scored on a Colt Snyder double and Ortiz and Snyder scored on an error that saw Billy Huyler reach first base.
In the bottom of the inning, Imperial's Antuñez got to first on an error, stole second and advanced to third on a fly out.
He scored when Ortiz tried to throw him out at home instead of going for the easy out at first that would have ended the game. Martinez scored one more run for Imperial to pull the score to 8-4, but when Daniel Ponce was thrown out at third trying to steal, the victory was sealed for Sunset.
Sunset advances to the championship game, where it will face unbeaten El Centro.
"We knew we were going to be matching up against them again," said Buchanan.
"The mental mistakes are going to make a difference in the outcome of the game," he added, noting he thinks neither team is necessarily better than the other.
"I don't think they're going to beat us pitching-wise or hitting-wise," Buchanan said. "We line up with them exactly the same,"
Ortiz said he is optimistic about facing the only team to which Sunset has lost in the tourney.
"I just want to beat El Centro," Ortiz said. "We want to beat them."
Sunset will face El Centro at 7 tonight at Rodriguez Field in Calexico.