Leading Sydney to Hobart yacht race contender Wild Oats XI has been struck by lightning in a big blow to its chances ahead of the gruelling bluewater classic, it was revealed Wednesday.

The supermaxi, an eight-time winner which was forced to retire from last year's race over a hydraulics issue, was in Sydney when a bolt of lightning hit the top of its 45-metre (147-feet) high carbon fibre mast.

Race organisers said a large number of electronic instruments were destroyed, all of which are vital if it is to maintain maximum speed and stay on course.

The boat will be put through its paces Wednesday to see if any of the carbon fibre rigging was damaged.

"It's a major blow for us on the eve of the big race," said Wild Oats owner Sandy Oatley.

"However, I'm sure our great team will have everything ready for the start on Boxing Day. There is no stopping them."

Another line honours favourite, Comanche, was docked alongside Wild Oats when the storm struck on Sunday, but escaped any damage.

The fleet for the 73rd edition of the often brutal 628-nautical mile (1,163-kilometre) race across the Tasman Sea will leave Sydney on December 26.

Australian supermaxi Perpetual Loyal, a long-time rival to Wild Oats, smashed the record last year, arriving at Hobart's Constitution Dock in 1 day 13hr 31min 20sec.

In a gesture to ensure Wild Oats can start, fellow supermaxi Black Jack has offered some of its own equipment from its warehouse in Brisbane.

"That's the spirit that exists in this level of ocean racing," said Oatley.

"We might be arch rivals on the race course, but we're all supportive of each other when necessary."

Wild Oats' skipper Mark Richards said he was hopeful the yacht will be ready.

"I'd like to think that this is the third strike when it comes to bad luck for Wild Oats XI in the Hobart race," he said.

"Two years ago the mainsail shredded in a storm; last year the canting keel hydraulic system keel failed, and now we've been hit from the heavens."

There are 103 entries this year for one of the world's most challenging races, including 28 from overseas.

Storms are a regular hazard with six men dying, five boats sinking and 55 sailors rescued on a fatal night in 1998 when a deep depression exploded over the Tasman Sea.

Source: AFP