It was a keen decision, considering that he has his hands on the wheel of one of the most mind-blowing sailboats ever built.

When the 33d America’s Cup begins tomorrow in this Mediterranean port, weather permitting, the boats will be the stars.

And boy, can these beasts fly.

Spithill will steer USA, a 90-by-90-foot trimaran representing American challenger BMW Oracle Racing of San Francisco, which is owned by software magnate Larry Ellison. It will try to wrest the oldest trophy in international sports away from two-time defending champion Alinghi of Switzerland, whose equally massive catamaran, Alinghi 5, could be steered by syndicate boss Ernesto Bertarelli or Ed Baird of St. Petersburg, Fla.

They are the fastest, most powerful and downright extreme boats in the 159-year history of the America’s Cup. When they hook into even the slightest breeze, their windward hulls fly off the water by up to 20 feet.

Capable of sailing at up to three times the speed of the wind, USA has flirted with 50 knots. Conventional America’s Cup yachts average 11 or 12 under good conditions.

BMW Oracle Racing kept pushing the limits late last year when it added a radical wing sail, which towers 223 feet off the deck.

The multihulls are the byproduct of a bitter, 2 1/2-year legal fight between Ellison and Bertarelli, two of the world’s wealthiest men. Though convoluted and contentious, the court case has brought the stodgy old America’s Cup decidedly into the 21st century.

“I think it’s probably the coolest part of this whole exercise, given that we’ve had to go through the courts and there’s been that sort of, I guess, a downer,’’ Spithill said.

“But the real upside is that thing,’’ he added, motioning toward the black-and-white, triple-hulled giant. “Whatever happens, this is always going to be something that’ll be really cool to be a part of.’’

If the best-of-three series is as spectacular as the participants think it can be, the boats might just restore some dignity to a sport that has been sullied by a tit-for-tat squabble between the powerhouse sailing teams over rules, dates, the venue, and practically everything else relating to the regatta.

The genesis of the spat between Ellison, the CEO of Oracle Corp., and Bertarelli, a biotech tycoon, was each side’s interpretation of the Deed of Gift, the 1887 document that governs the America’s Cup.

Interestingly, it is that same 19th century document that provided the simple parameters for the two giant multihulls.

The America’s Cup normally is contested in sloops that are approximately 85 feet long, with several challengers competing for the right to face the defender. Because Alinghi and BMW Oracle Racing couldn’t agree to rules for a conventional regatta, it defaulted to a rare head-to-head showdown, or Deed of Gift Match.

According to the Deed, boats with one mast have one basic design limitation: They can’t be less than 44 feet or more than 90 feet on the waterline when the vessel is fully loaded.

When BMW Oracle Racing issued its challenge in July 2007, it specified only a boat with a 90-foot load-waterline and a 90-foot beam, or width. Just in case the two sides couldn’t come up with a mutually agreed class rule - and they didn’t - the Americans weren’t going to make the same mistake New Zealander Michael Fay made in 1988. He challenged Dennis Conner with a 90-foot monohull, and was routed by Conner’s smaller, much faster catamaran off San Diego in the only other Deed of Gift Match in modern times.

So when the Americans specified a 90-by-90-foot boat, everyone knew their intention was going to be a multihull. What kind was up to each team.

The Americans chose a trimaran, feeling a triple-hulled boat would be a good, all-around platform for light air and flat water, and would have been OK had the Swiss picked a port that had stronger wind and waves.

“Multihulls have been faster than monohulls since whenever the Tahitians strapped two logs together,’’ said New Zealander Mike Drummond, BMW Oracle Racing’s design director.

Alinghi chose a classic two-hulled boat based on a smaller catamaran Bertarelli had sailed on Lake Geneva.

The scale of these boats is off the charts.

Plop USA down on the infield at Yankee Stadium and it would cover each base and home plate.

Alinghi 5’s trampoline, the mesh material that serves as the deck, is twice as big as a tennis court.

These boats are dream projects for designers and engineers. There will be talk during the regatta of the lift coefficient of a wing and of the boats’ power-to-weight ratio. But even the sailors can’t ignore the simple “wow’’ factor.

“To do it on this scale is something pretty amazing,’’ said BMW Oracle Racing skipper and CEO Russell Coutts, a three-time America’s Cup winner. “I don’t think we’ll see the same thing again in our lifetimes.’’