Grant Wharington has declared his supermaxi Wild Thing 100 a better chance of winning the Sydney to Hobart on handicap than claiming the line honours prize usually contested by boats her size.

But her rivals are not so sure, insisting the boat that bumbled its way to the starting line last year is a genuine threat of reaching the finish line first this time.

Wild Thing was the surprise packet of last week's Big Boat Challenge on Sydney Harbour, the last competitive hit-out before the big race on Boxing Day.

The 100-foot supermaxi shot out of the blocks to push hot favourite Comanche, ultimately crossing the line third, but putting her rivals on notice.

"I looked at the speed that thing was going at and I was amazed," Comanche co-skipper James Mayo said.

The Big Boat is a far cry from the 628-nautical mile journey to Hobart's Constitution Dock.

But the race gave Wharington a level of confidence completely absent last year, when he scrambled to add 20 extra feet of length to Wild Thing's predecessor, Stefan Racing, in time for Boxing Day.

"Last year to get to the start line was one thing, to get to the finish line was a whole next level," he told AAP.

"Our whole boat's been a work in progress over the last 12 months, but [in the Big Boat Challenge] we really proved that it's competitive."

Written off by one and all in 2023, Wharington still doubts his boat can push Comanche or LawConnect to reach Hobart first after the pair waged an epic tussle for line honours last year.

But his boat lacks some of her rivals' bells and whistles, meaning she will score better on handicap as race officials determine the overall winner.

Wild Thing's mast is smaller than that of Comanche or LawConnect, and it does not have water ballast, a system used to stabilise the boat and manipulate her weight mid-race.

It has left Wharington with his eyes on the handicap honours.

"I don't think it's realistic to think that we can be a line honours competitor this year," Wharington said.

"It's Comanche's race to lose [on line honours]. That boat was over $40 million, 10 years ago, to build. There's no other boat built to that level.

"But if it becomes a big boat race and we're within a couple of hours of those guys, that's enough to win the race [on handicap].

"Depending on the time, it's somewhere between four and six hours that Comanche has to beat us by and LawConnect maybe two to three hours. That's quite a lot of distance when you're travelling at 20 knots."

Wild Thing thrives in slightly different conditions to her rivals too, preferring when the wind is reaching — blowing from the side of the boat rather than as a direct headwind or tailwind.

In conditions like that, Comanche co-skipper Matt Allen says Wild Thing is a threat to his boat's line honours tilt.

"I think with the right wind angle they are," he said.

"If we get a reach to Hobart, which sometimes happens — the last time we had it was probably 2016 when we had a reach most of the way — she's pretty powerful on the reach.

"Probably upwind, downwind, LawConnect and Master Lock Comanche have got it over them, but they've got a point where they're really competitive."

AAP