Wild Oats XI has smashed the Sydney to Hobart yacht race record to win its ninth line honours title, beating Comanche to the line in the closest finish in decades.

Comanche crossed the line almost half an hour later, and followed through with a threat to lodge a protest over a near collision at the start of the race.

A five-member international jury gathered at the Royal Tasmanian Yacht Club in Hobart about 3:00pm (AEDT) on Thursday to rule on the protest.

They are taking evidence from crew members of both yachts and will inspect television footage of the incident.

The protest hearing has put the announcement of the Tattersall's Cup winner on hold. ( Facebook: Rolex Sydney Hobart )

If upheld, the protest could result in Wild Oats XI receiving a time penalty of five minutes or more.

The length of the hearing and deliberation has meant the official announcement of the overall winner of the race has been pushed back to Friday.

Currently Ichi Ban, which crossed in eighth position, looks set to claim the Tattersall's Cup for handicap honours, even though more than half the fleet has still to finish.

But the crew's nervous wait will continue overnight.

Comanche reached the River Derwent a few minutes ahead of Wild Oats XI but both were becalmed in the notoriously slow last leg.

The lighter Wild Oats XI was able to find more speed upriver to cross the line, and finished just 26 minutes and 34 seconds ahead of Comanche.

Skippered by Mark Richards, Wild Oats XI crossed the line about 9:50pm on Wednesday in a time of 1 day, 8 hours, 48 minutes and 50 seconds.

That was about four hours and 40 minutes faster than the record set last year by Perpetual LOYAL, which crossed the line at 2:31am.

When asked how he felt passing Comanche on the Derwent, the victorious skipper said he "couldn't bloody believe it".

"As a skipper, you're responsible for the whole thing … it's a big deal and you go through a massive cycle of thoughts during the whole race," Richards said.

"But to get the opportunity at the end there to have another crack at it and to finish it off with a race record was unbelievably special."

Comanche's hopes dashed

On Wednesday morning it was Comanche's race as it led the field down the east coast of Tasmania with Wild Oats XI trailing by about 20 nautical miles.

By the afternoon, the two boats were neck and neck, charging down the coast at up to 30 knots, care of a stiff north-easterly.

Wild Oats XI overtook Comanche before the lead chopped and changed as they rounded Tasman Island and made for the Derwent.

In the afternoon Wild Oats XI and LDV Comanche were neck and neck. ( ABC News: David Robertson )

There they ground to a near halt, but the lighter boat made the most of its advantage and opened a winning lead.

Richards credited the state-of-the-art Comanche with being "unbelievably fast" but said they became powerless when the wind abandoned them.

"But all that power doesn't come for free and [on] the Derwent River the one thing you didn't need is all that power and that's where the little narrow Wild Oats slipped away," he said.

The win ends a run of bad luck for Wild Oats XI, which had to retire from the past two races.

Its mast broke in 2015 and a hydraulic ram failure forced it out last year.

Sorry, this video has expired Leaders charge towards Hobart in record time ( ABC News )

Richards shrugs off protest

With Comanche's protest pending, the dockside celebrations in Hobart were subdued with no medals being handed out.

The protest was lodged in writing as per race rules when Comanche arrived at Constitution Dock.

But Richards shrugged off the prospect of a penalty, saying he did not order the boat to complete a 720-degree penalty turn because he felt they had done nothing wrong.

"If that was a blatant infringement then obviously we would do our turn but it actually wasn't," he said.

"In our minds we were clear ahead and we've got video footage to prove it.

"If you read the rule book we did the right thing and that's all there is to it."

'It was an obvious infringement'

Comanche owner and skipper Jim Cooney said he would leave it up to the panel of international judges to rule on the protest.

"It was a pretty obvious infringement of the rules, I am pretty confident of that," he said.

Comanche skipper Jim Cooney. ( ABC News: David Robertson )

"I guess if you are the one in the wrong you would play it down, but I'll leave it to the jury."

Comanche helmsman Jimmy Spithill focused after the race on the fickle nature of sailing the supermaxis up the River Derwent stretch of 11 nautical miles.

Spithill said it was now off to the "protest room" where it would be up to the jury.

"We felt they broke a rule and it looked like they fouled us … We looked at some of the TV footage and it looked like they fouled us.

"It cost us significant time."

Five of the supermaxis in this year's fleet finished inside the record for the 638 nautical mile race.