Wi, 18, Wins State Amateur Title : Golf: Recent Westlake High graduate closes out Vanier, 3 and 2, with some clutch play on the second 18 holes at Pebble Beach.

PEBBLE BEACH —  It was damp and chilly early Friday at the Pebble Beach Golf Links. But Charlie Wi stayed hot all day.

Wi, 18, who graduated two weeks ago from Westlake High, completed a magnificent weeklong stretch of golf by winning the 79th California Amateur Championship, finishing off former Stanford star Gary Vanier, 3 and 2.

Wi, of Thousand Oaks, failed to qualify for the tournament and slipped in as an alternate when the NCAA champion, Arizona State’s Phil Mickelson of San Diego, withdrew to attend an NCAA awards dinner in New York.

After a poor start Monday, when he shot a 75 at Cypress Point in the first round of stroke play, Wi came back with a 68 at the Monterey Peninsula Country Club Tuesday and entered match play as the No. 3 qualifier.

He eliminated two players in Wednesday’s opening session of match play. On Thursday, he first ousted veteran Craig Steinberg of Van Nuys, a former winner of the event who had advanced to the quarterfinals for the third consecutive year, and then Paul Stankowski of Oxnard, the 1989 Southern California Golf Assn. amateur champion.

Vanier, 39, an Oakland stockbroker who played on the same Stanford team with Tom Watson, had won the State Amateur in 1982 and had made it into match play in the event 10 times.

But he was no match for Wi in the 36-hole final.

The South Korea-born Wi made a 45-foot birdie putt on the fourth hole not long after daybreak to go 1-up on Vanier. He increased his lead to 3-up on the 18th hole when Vanier’s tee shot found the most disturbing hazard a golfer can confront, the Pacific Ocean.

Wi went 4-up by winning the first hole of the second 18, but Vanier charged back, evening the match by winning four holes with an eagle, two birdies and a par on No. 6 when Wi missed a short putt for par.

But Wi, who will attend Nevada Reno on a golf scholarship, took the lead again on No. 7 and never lost it. He won the 10th, 11th and 12th to take a commanding 4-up lead and, after losing the 15th with his only errant tee shot of the day, closed out Vanier with a par on No. 16.

“I really didn’t think I could win,” Wi said. “I just wanted to make it to match play. I didn’t believe I could win until today, and only after the first 18 holes today, when I was 3-up.”

Wi’s caddy, former Westlake High golf teammate Jeff Rulon, said the turning point came when Vanier evened the match.

“The best thing Charlie did today was, when Vanier got even, Charlie pretended he was down three holes, not even,” Rulon said. “From then on, he played more aggressively and stopped laying back.”

As Wi, who turned 18 two months ago, sat with a group of reporters and excitedly recounted his week, a disgruntled Vanier sat for a few moments and listened.

Then, Vanier got up and, for the first time all day, did something that Wi could not do. He walked into the tavern at Pebble Beach and drank a beer.