Wild Oats XI will be gunning for an unprecedented ninth line honours title in the Sydney to Hobart.

The Sydney to Hobart's two star supermaxis Wild Oats XI and Comanche have been forced to withdraw from the iconic race as strong winds hit the front of the fleet on the first night.

Eight-time winner and defending champion Wild Oats XI retired late on Saturday night with a torn mainsail while soon after Comanche, who was leading, pulled out with a broken rudder.

Last year, record-breaking Australian yacht Wild Oats XI pipped her 100-foot American rival by just 55 minutes to add to her bulging trophy cabinet.

A strong southerly change - which brought winds of up to 43 knots - hit the fleet's frontrunners on Saturday night along the NSW south coast just over 10 hours after the start of the race in Sydney Harbour.

"Early reports indicate that the sail tore in half when the yacht was hit by a 40 knot squall that accompanied a southerly change off the NSW south coast," said the Wild Oats XI statement.

All crew are safe and the yacht will return to Sydney.

Comanche reportedly pulled out with a broken rudder and damaged dagger board.

Wild Oats XI, skippered by Mark Richards, is the most prolific winner in the race's 71-year history, and set the race's fastest time in 2012 of one day, 18 hours, 23 minutes and 12 seconds.

Alfa Romeo II (2009) and Investec Loyal (2011) are the only two boats to break Wild Oats XI's stranglehold on the race since 2005.

American boat Comanche was in first place after taking the lead from Perpetual Loyal soon after exiting Sydney Heads.

Fellow supermaxis Ragamuffin 100 and the celebrity-laden Perpetual Loyal will now be the hot contenders for line honours, as will another US raider in Rambler 88.

Prior to Wild Oats XI's withdrawal, five boats had already retired back to the Cruising Yacht Club of Australia in Sydney wearing wounds.

Tasmanian boat Cougar II returned with the most damage after an incident with Lupa of London left her without an entire corner of her stern.

No one was seriously hurt, although one sailor suffered facial cuts.

"Unfortunately the boat that clipped us was quite big," said crew member Mike Feilberg.

"There was more damage to top of the mast, significant damage. We're fairly lucky that there wasn't any more serious injuries."

The captain of the British 78-footer, Laurent Pages, described it as a "stupid accident".

"We were sailing on starboard tack from the start and three boats got locked together - we were in the middle with nowhere to go," he said.

"We were left with the decision to run into the boat above us or the one below us. This was the worst feeling - a stupid accident.

"The race committee told us all to take it easy at the start - there was a whole race to go.

"If everyone listened, this would not have happened. We are shattered."

Chinese boat Ark323, on her Hobart debut, came back with a crack in the deck after a prang with a rival yacht, while a forestay snapped off the top of the Perth-based M3's rig.

Newcastle 47-footer Dare Devil also retired later in the day.

The race entrants weren't the only ones to crash out early, with start boat Aussie Legend forced into an emergency evacuation of its passengers at Taronga Zoo wharf when it began taking water.

Officials had to revert to using an old-school horn instead of the traditional firing of the cannon.