America 3 Needs One More : Sailing: Koch’s boat shows superior speed in taking 3-1 advantage over Il Moro di Venezia.

A fast, new boat is telling the same old story in the America’s Cup--the United States is very tough to beat.

Superior boat speed carried America3 within one win of the country’s 28th Cup victory in 29 tries as it beat Italy’s Il Moro di Venezia by one minute, four seconds Thursday.

Leading 3-1, America3 can clinch the best-of-seven series Saturday and maintain America’s dominance in the 141-year-old event.

The crew’s mood is “very, very cautiously optimistic,” America3 Foundation president and co-helmsman Bill Koch said. “We think we have very good boat speed. We have great confidence in our crew and our tactician (Dave Dellenbaugh) and our boat handling. All we have to do is keep it together.”

Had the Americans done that in last Sunday’s second race, the series might be over. They made up all of a 31-second deficit on the final leg, then botched their last jibe near the finish line and lost by three seconds.

Their crew work was much better last Tuesday in a 1:58 blowout and stayed sharp Thursday.

America3 was one of the syndicate’s four boats in the trials, which began Jan. 14. It wasn’t launched until early February.

It led by 47 seconds two legs into the eight-leg, 20.03-mile race off Point Loma. Then Il Moro skipper Paul Cayard ate into that on the third leg, into the wind, and trailed by 27 seconds at the mark.

“We were 11 boat lengths ahead, then we went down to about two boat lengths ahead,” Koch said. “Part of it was we think we had up the wrong sail at the time. But then the rest of it was boat speed.”

Poor sail choice may have hurt Il Moro more.

It won the start by one second but may have paid for its decision to use a mainsail that was narrower at the top than America3’s. Il Moro’s sail is preferable in winds of 13 knots and stronger, but the westerly breeze dropped from about 12 knots at the start to about 8.5 knots early on the second leg.

By the end of the first leg, against the wind, America3 had a 24-second lead. Buddy Melges had taken over the wheel after Dellenbaugh handled the start.

“I’m not sure they would have used the same mainsail” if they could make the choice again, Dellenbaugh said of Il Moro’s crew.

While Il Moro teeters on the brink of elimination, its predicament is not insurmountable.

In the challenger finals, it trailed New Zealand 3-1, then won the next four races in the best-of-nine series to become the first Italian finalist ever and first European finalist since 1964. But America3 is faster than New Zealand.

In the 1983 America’s Cup, the only time the United States lost, Australia II trailed Liberty, 3-1, then won the next three races. But Australia II was much faster than Liberty.

Il Moro is not faster than America3.

“We can do it” Saturday, Koch said, “but we’re not planning on it. We’re planning for a tough series.”

After losing 20 seconds on the third leg, America3 won the remaining five legs. It added slightly to its lead on legs four through seven, then won the last leg, downwind, by 28 seconds.

One of America3’s scariest moment’s came at the end of the sixth leg when grinder Peter Fennelly’s leg got caught in the jib sheet, a rope used to trim the sail, and he apparently went in the water. He was helped back by crew members Wally Henry and Jerry Kirby.

The U.S. boat began the race to the left of Il Moro, the same positioning as in Tuesday’s victory. But the Italians aligned their boat closer to America3 than they did Tuesday, when they were too far to influence America3’s movements.

On the second leg, with the wind, America3 built its lead to 47 seconds. It was the fifth time on the first seven downwind legs of the series that America3 had gained. The U.S. yacht also used a gennaker sail in front of the boat, designed for winds under 10 knots, while Il Moro went for a spinnaker, more suited to stronger breezes than those during that leg Thursday.

There are three upwind legs per race, and America3 had made big gains on four of them in succession in Races 3 and 4.

But Cayard, a San Francisco native, mounted his first significant challenge Thursday when he broke that streak on the third leg. A tacking duel helped Il Moro eat into the 47-second lead with the help of stronger wind on the left side of the course.

But the U.S. yacht solidified its lead, gaining 3, 2 and 2 seconds on the next three legs, all reaches in which the wind comes over the side of the boat. It added two seconds to lead by 36 seconds after the seventh leg.

America3 won the first race by 30 seconds, then lost Race 2 in the closest finish in Cup finals history. It came back with Tuesday’s crushing win.

Although Il Moro was first across the starting line in Races 3 and 4, it has trailed America3 at all 16 marks throughout those races.