Two existing Sydney to Hobart race records are under threat following a favourable weather forecast for the fancied big boats.

The fleet of 85 was on Saturday tipped to expect "pretty light" five to 10 knot east to southeasterly breezes for the Boxing Day afternoon start, with freshening nor'easters to send the boats zooming down the southern NSW coast from Monday night until probably Wednesday morning.

While a cold front on Wednesday is expected to bring strong to gale force westerly winds, the brand new super maxis, Alfa Romeo and Wild Oats XI are likely to have reached Hobart, along with their slightly older big boat rivals, Skandia, Konica Minolta and AAPT2, which took line honours last year as Nicorette.

"I think if those conditions are here, I'd say all five boats will break the record," said Mark Richards, the principal helmsman on Wild Oats XI.

Richards was referring to the open race record of one day 19 hours 48 minutes 2 seconds set by Nokia back in 1999.

"The record definitely I reckon is gone, even with sailing up against the wind going up the Derwent," said Sean Langman, skipper of AAPT2.

"I'm pretty excited, it's just like my kids have got one sleep before Christmas, we've got two sleeps to (the start of the Sydney to) Hobart."

Langman thought there was even a chance of a boat completing the rare treble of line and overall honours and a new race record.

Nokia's mark was the best for a boat with legitimate water ballast, but Cruising Yacht Club of Australia chief commodore Geoff Lavis pointed out Brindabella held a separate record for a conventional yacht of one day 20 hours 39 minutes 50 seconds also set in 1999.

Richards however issued one cautionary note.

"The forecast sounds fantastic but we've heard that before and things have changed overnight," Richards said.

Alfa Romeo's owner Neville Crichton revealed his drivers and trimmers would be outfitted with crash helmets as his swift yacht was expected to at times match if not better Nokia's speed of around 30 knots six years ago.

"I think the boat is capable of a lot more than 30 knots, but it's one thing doing 30 knots and another thing averaging 30 knots," Crichton said.

The potentially strong to gale force westerly winds tipped for Wednesday are likely to subside and give way to a fresh batch of northerly breezes on Thursday, which would then assist boats in the back half of the fleet.

Lavis anticipated the middle ranking boats would be the ones that would struggle the most as they were the ones most likely to be affected by the front bringing the predicted strong to gale force westerly winds forecast for next Wednesday.

"In reality it looks like a big boat and little boat race, I think the middle of the fleet is going to find it tough," Lavis said.

Brought to you by AAP © 2024 AAP