The score was tied at 1 heading into the bottom of the sixth. Cordeiro connected on an outside pitch from Mariners pitcher Kaylee Carlson and ignited a three-run inning for the Vikings.
"My coaches came up to me and said, 'you're due,' " said Cordeiro, who had two hits Friday when Marina won, 4-2, in a first-round game at Redlands. "When I hit it, it felt great and I knew we'd score. I was just happy to be able to contribute."
The victory sends Marina, which tied for second with Edison in the Sunset League but is the league's No. 3 entry in the playoffs, into a quarterfinal game Thursday. The Vikings (21-6-1) will host Santiago of Corona, winner of the Big VIII League title, at 3:15 p.m.
The Sharks on Tuesday were a 6-2 second-round winner over West Ranch (Foothill No. 2).
"I'm so proud of this team," Marina Coach Shelly Luth said. "The girls are playing solid softball and really are showing confidence. Earlier in the season, we had trouble closing games. Now, we're playing to the end, all 21 outs."
Senior Jamie Sullivan gave the Vikings a shot of adrenaline by roping a double up the left-center field gap to lead off the Marina sixth. Tera Blanco drew a walk and Kristen Struett hit a grounder to third base that the Mariners misplayed on a throw to second, which loaded the bases. One out after Cordeiro's two-run single had put the Vikings in the lead, her younger sister, Keala, dropped a single into shallow right field that scored Struett to make it 4-1.
Keala Cordeiro, who impressed Luth in practice toward the end of the regular season, has been the Vikings' designated hitter during the playoffs.
Blanco went the distance for the win and ran her record to 18-6. Luth said the freshman will start Thursday against Santiago.
Ocean View reaches quarterfinals