The Sea Kings had just played the best match of their season.
Parker Brown led the way with 28 kills, and he clinched the win with a kill in the decisive fifth set.
The junior tried to blow the ball through a wall the previous time CdM had match point. With another chance, he delivered.
"We wanted it more," Brown said.
The timing of the big win is ideal for CdM Coach Steve Conti with the CIF Southern Section Division II playoffs starting next week.
The Sea Kings (25-4) will be the top seed when the section releases the playoff pairings on Sunday. To Conti, they finally played like a top-ranked team.
"This does a lot for us because we haven't been playing very good volleyball lately," said Conti, whose team won the Pacific Coast League title. "We've been winning, but we haven't been playing volleyball like we played [Friday]. This is a good sign.
"I'm really proud of our guys. We played [the Sailors] twice [earlier in the season]. They manhandled us both times. We ran a little bit better of a game plan this time and it is about as good as our guys have executed a game plan all year."
The Sea Kings got contributions from practically everyone. Nick Curci and Joe Ctvrtlik set the offense, finding Brown and Evan Dean.
Dean came up with huge kills, finishing with 19. When CdM needed a block, Stanford-bound middle blocker Spencer Haly stepped up.
Haly was busy as outside hitter Cody Caldwell kept blasting winners all over the court for the Sunset League champion Sailors. Caldwell recorded a match-high 35 kills and added 17 digs.
But the Sailors (22-8) depended too much on the 6-foot-6 senior. Rusty Sary helped with 20 kills, but the Sea Kings' defense focused on the two senior hitters.
The annual rivalry match could have gone either way. The Sailors, ranked No. 4 in the Division I coaches' poll, fought back after seeing CdM slip past them in the first and third sets.
The opening set was competitive and it only featured two ties. The second set saw 20 ties, the third set 18 ties and the fourth set 18 ties.
The final set was even seven times, until the Sea Kings went on a 6-2 run to finish any chance Newport Harbor had of staying perfect against Corona del Mar this year.