The biggest risk," Jim Hardy shouted across the din of the bustling shipyard at Newport Offshore, "is to take no risk at all."

Hardy, the gentle skipper of the yacht Australia, and his 10 mates prepared today to take the biggest risk they could find when they put to sea in quest of the America's Cup.

They face the American yacht Freedom in the start of the best-of-seven final Cup series Tuesday. The outlook for the challengers is far from positive.

"Shaky," said a woman follower of the Australian campaign. "They look very shaky."

In years past when observers said the Australians looked shaky they generally meant it literally. The folks from down under have earned a reputation for hard drinking, late carousing and good sailing over the last 18 years as they won the right to challenge in five of the last six Cup seasons.

But this year the Aussies have lowered their profiles. A sign in their office says, "If you want to soar with the eagles in the morning you can't hoot with the owls all night." The rough-and tumble crewmen evidently have taken that message to heart.

Still, they're about to embark on their biggest risk.

A little over a week ago, a new state-of-the-art, whippy-topped mast was installed on the Australia. It was to be a great secret weapon, designed to disarm the Americans and provide a winning edge in the racing.

But all it provided in the week the Aussies had left to test it was top- flight training in how to remove and replace disabled masts.

"We have a new record," bowman Scott McAllister exulted today as the mast was plopped back in the yacht for the third time in a week. "Thirty- three minutes, seven point two seconds."

"They are getting good at it," said John Sparkman of the Freedom camp. "They ought to be by now."

The difference in the Freedom and Australia camps today was the difference between breakfast at home on a sleepy Sunday and breakfast at the Times Square Chock Full o' Nuts during weekday rush hour. While Dennis Conner's crew luxuriated in the comfort of everything done that needs to be done, the Australians battled with more last-minute details than the participants in a shotgun wedding.

Australia and Freedom are docked within sight of each other, across a maze of pleasure boats in Newport harbor. With a cold norther blowing, the Freedom crew held off making its final practice run until almost noon today.

They spent much of the morning taking stock of their huge sail inventory in a shed near the docks. Two sail company presidents, John Marshall of North and Tom Whidden of Sobstad, went over with skipper Conner a list of some of the 80-plus sails Freedom has tested and used.

Freedom has so many sails that last week notices of "sails available" were left on big yachts in the harbor.

So Conner, Marshall (Freedom's sail tactician) and Whidden (the port winch tailer) had to break off discussion briefly while a prospective buyer ran over a list with them.

"We have," said Whidden, "an embarrassment of riches."

While Freedom was having a yard sale, McAllister and Hardy and the boys from Australia were scampering up their mast, organizing lines and cables, halyards and sheets, and wondering whether the newly recut sails will fit on the mast when they go up this time.

On Sunday, they hadn't been sailing an hour and a half when a section of the jumper strut, a large fitting near the top of the mast, bent in half.

Then the mainsail fouled in its track and the boat had to come home in disarray, under tow, her sail half-flying.

After the mast was pulled, Australia's crew spent until 11 p.m. Sunday night unfolding the mess, while Freedom's happy throng was toasted and presented with free watches at an elegant cocktail party.

Early this morning, the repaired Australian mast was reinstalled, but a hydraulic gizmo used to set up the rigging blew up and the installation stretched on to close to noon.

The decks of Australia were dirty, her insides were fouled with hydraulic oil, half her sails didn't fit, and the crew was wondering, "What next?"

Freedom hasn't had one instance of significant gear failure since the trails to select a U.S. defender began in June. Australia has had one problem after another, barely defeating a slowpoke Swedish boat for the right to challenge.

Now her secret weapon is giving her fits.

"It's really a shame," said Rich duMoulin, son of the Freedom project manager and a former America's Cup crewman. "We'd like to see them go out and race on their own merits, win or lose. We hate to have it be a gear failure thing."

After the Sunday debacle the Aussies had a grim meeting on their yacht, then broke into work parties.

"What are you going to do now?" onlookers demanded of project manager Warren Jones.

"Pull the bloody mast again," he said.

"And throw it away?"

"No, Fix it," he hissed.

With all signs pointing to a rout on the water, there yet remains the incontestable feeling that turnabout is not impossible.

"Remember, these are two boats that have never sailed against each other," said Rives Potts, Freedom's Popeye-muscled middeck man.

"Anytime you meet a boat for the first time you wonder how it will go."

Sometime afternoon on Tuesday, the mystery will be over.