Cannons blasted, horns blared and a single champagne cork popped this afternoon when the 12-meter yacht Australia returned from sea.

But on the dock next door where the French came home almost simultaneously it was silent as an empty church.

Backs to the wall, the Australians hammered the Swedish boat Sverige today to win their semifinal America's Cup series. The victory sent the Swedes home and advanced the Australians to a berth in the challengers' final series, beginning Friday.

They will meet France, which had to survive a protest from the English before being declared the winner.

France III managed a convincing win over the British boat Lionheart aswell. But the gloom that hung like dirty air when the French returned tolddifferent tale.

France III led Lionheart all the way around a 24.3 mile course today in a building breeze. The win should havegiven the French the best-of-seven series, 4-2, and pitted them against theAustralians in the upcoming final.

But from the backstays of both British and French yachts red flage dangled all day, symbols of protests on which the day's results would hang.

France III and Lionheart collidedduring racing today, as they have twice before in this series. France claimed the crash at the start was Lionheart's fault. Lionheart said it was the French crew's mistake.

The decision on who was at fault was left in the hands of an international protest jury, which convened late tonight to hear the evidence. From all appearances among the French,their hopes were not high.

It wasn't until after 11 o'clock tonight that an international protest jury heard the evidence that declared France -- to the surprise of almost everyone involved -- the winner. Said French skipper Bruno Trouble, "You lose some you're ready to win and you win some you're ready to lose."

Then, in the pitch black on Goat Island outside the International Yacht Racing Headquarters. Trouble's crewmates hoisted him and tossed him fully clothed into the harbor. The protest committee said France was not given adequate room by the British to avoid the collision.

Lionheart and France III were engaged in the standard sparring behind the start that precedes most match sailboat races. With only a few minutes remaining before the start the Britons began a wide turn toward the line.

The British yacht jibed and France III skipper Trouble seemed intent on duplicating the maneuver. He swung his yacht alongside Lionheart, but the gap closed and the masts of bothyachts shook when they met.

France retained the favored position and when the starting gun went off she had an edge of 14 seconds. She never relinquished the lead, building on it as the day progressed.

The protest issue had left the French crew troubled throughout the racing, yet when it was over and they had crossed the finish line 54 seconds ahead of the black British boat, they alowed themselves a brief Gallic flourish nonetheless.

Baron Marcel Bich, the ball point pen magnate who has spent 10 years and countless millions in his quest for the Cup, stood up in his white linen suit and waved his white cap to converging boats. He took the helm of France III and, with great fanfare, heaved the chapeau overboard.

Bich did not go bareheaded for long. He had a spare handy. The Australian victory was a walkaway.They have long been recognized. as the fastest of the foreign boats, andSverige as the slowest. But in two straight races, gear breakdowns handed the Australians defeats. Today, with the series tied and in sudden death, winner take all, they kept gear together and buried the Swedes, finishing 8 minutes 18 seconds in front.

"We were able to sail higher (closer to the wind) and faster than they could," said Australia skipper Jim Hardy afterward. "Believe me, that's a beautiful feeling . . ."

The two remaining American boats also were at sea. On Monday, defending champion Ted Turner and his boat Courageous were excused from the competition, leaving Dennis Conner's swift Freedom and Russell Long's 4 month-old Clipper to vie for the right to defend the Cup.

Today, for the first time in these final trials for American boats, Clipper took one race from Freedom, sailing past her rival on an upwind leg after losing the start.

In two other races the heavily favored Freedom swept to victory by margins of 1 minute in the first race and 27 seconds in the third. All the U.S. races were on shortened courses in winds that built from about 6 knots at the start of the day to 12 at quitting time.