Courageous, the born-again 12-meter with a crew of youthful unknowns, scored three stunning victories in America's Cup races over stablemate Defender today, leaving her the runaway early leader in trials to pick an American defender.

The wins by the refurbished two-time cup champion were so convincing that Defender tactician Gary Jobson all but threw in the towel at day's end.

"Courageous is going extremely well," he said. "Defender's goal now will be to make sure they (Courageous) keep going as well as they can."

The comment was remarkable in view of the fact Defender remains in the running to defend the cup. But Jobson said Courageous' speed under young skipper John Kolius is so clearly superior to Defender's that the Defender/Courageous group will commit itself to helping Courageous in the effort to unseat defending champion Dennis Conner.

"I think our group will beat Dennis, and that's good for the sport," said Jobson.

It puts a sudden spotlight on the 32-year-old Kolius, a small-boat sailor who two years ago had never raced a 12-meter. When newsmen asked if the hurricane which struck his native Houston damaged any of his yachts, he said, "The boats I have did fine. They were in my back yard--a Sunfish, a Laser, little stuff. I don't own a big boat."

If the idea of a Sunfish skipper competing in the most sophisticated class in all yacht racing sounds odd, try on for size the notion of the Sunfish skipper winning.

"At this juncture," Kolius maintains, "Courageous is the fastest (American) boat. To lose (in trials to select a cup defender) we either have to sail badly or the other boats will have to adjust better than we do."

With her 6-1 record in final August trials, Courageous is far ahead of Conner's Liberty (2-2) and Defender (1-4). Kolius has taken the aged yacht so far beyond expectations that knowledgeable observers say if he won not another race all summer, he'd still be assured of a new boat and a well-financed campaign in the next cup year.

Kolius has won the admiration of the America's Cup selection committee by avoiding the politics and personality disputes that have sullied this cup year for the other two American contenders.

This weekend, for example, the New York Yacht Club commodore had to retract an injudicious remark made by Conner, who publicly accused challenger Australia II of "sandbagging" a race.

Conner and Tom Blackaller, the Defender skipper, rattle each other. Their meetings on the race course frequently erupt into protests and squabbles, tying up their and the race committee's time and energy.

Conner has been mounting a political side campaign against the Australians, seeking to have their radical new keel disallowed.

It adds up to a bellicose and distracted scene among the Americans, except for Kolius and his crew, who quietly work on their 10-year-old boat, sail enthusiastically and generally seem to enjoy themselves.

"John's operation is a lot like Conner's was last time," said Lexie Gahagan, who was Conner's bowman in 1980 but gave up cup racing to start a business.

The guys are real close. They figure they have everything to gain and nothing to lose."

By contrast, Conner's outfit has become "bigger, more like a syndicate and more businesslike," said Gahagan, adding that if he had a choice of boats to join he'd pick Courageous, even though Conner remains the favorite.

The sandy-haired Kolius is more than a Sunfish sailor, of course. He's twice J-24 world champion, an Olympic sailing silver medalist in 1976 and manager of the Ulmer sail loft in Houston. In recent years he's broadened his horizons by ocean racing on other people's yachts.

He signed on Courageous less than two years ago as a sail-trimmer, then won a shot at the captain's job when original skipper Dave Vietor backed out 18 months ago.

In California last winter Courageous was a whipping boy for Defender, losing race after race in training. But by spring, profiting from a crew "learning curve" Liberty tactician Tom Whidden says is the best he's seen, the boats were approaching parity.

The learning curve had to be sharp, Kolius said, because only one crew member had sailed a 12-meter before.

"Sailing the boat was no problem," said Kolius, "but making decisions we knew nothing about was. Stuff like, should we have bigger shrouds? On big (ocean racing) boats you can ask the designer. We had to worry about all that ourselves, and I knew nothing about it."

Bit by bit they figured out what made a 12 go, he said. "I still like to work on the boat with the guys, to see how it works. I hope they don't mind. Once in awhile they say, 'God, you really don't know what you're doing.' I say, 'No, I'm just learning like everyone else.' "

Cheered on by a crowd of Texans who have descended on Newport in his honor, Kolius and his band of neophytes managed to reverse a poor showing in the July trials with three quick victories at the start of the August final trials to pick a defender. Then came today's whitewash.

But this is the sudden-death phase of the trials, when a yacht can be dismissed by the selection committee at any time. In Kolius' eyes, a few quick wins is more dangerous than a loss or two. He remains ever vigilant.

"In this game," said Kolius, "if you win a couple of races and just stay level, the others will roar right by you."