Queensland boat Black Jack has a handy lead over early favourite LawConnect in the race for line honours on day one of the Sydney to Hobart yacht race, with tough conditions forcing more than a dozen starters to retire. 

Racing under the flag of the Yacht Club de Monaco, Black Jack had an advantage of 13.6 nautical miles over LawConnect as of 1:00am AEDT.

LawConnect, a supermaxi, was one of the pre-race favourites and held the lead earlier on the opening day.

It won line honours in the 2016 edition, racing as Perpetual Loyal.

The 80-footer Stefan Racing was a further 1.3 nautical miles behind, and SHK Scallywagg was another 4.3 nautical miles back in fourth.   

The forecast was for strong southerly or southeasterly winds for the first 24 hours or so of the race, with the possibility of much lighter winds later on, slowing the fleet down crossing Bass Strait.

Fifteen starters were forced to retire on day one, including NSW boats Blink, Mako and Mille Sabords, White Noise from Victoria and Tasmania's Oskana.

The line honours race record, set by Comanche in 2017, of one day, 9 hours, 15 minutes, 24 seconds, is not under threat.

Early predictions were that the leaders would not reach the finish line in Hobart in under two days.

The start was fiercely contested, with the three supermaxis — LawConnect, Black Jack and SHK Scallywag — all in the mix.

The Hong Kong-based Scallywag, skippered by David Witt, made the best start, and took the lead on the run to the opening mark.

The supermaxi made it to the heads in a little over 5 minutes and navigated the opening mark well with Black Jack right behind.

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However, the problems started soon afterwards, as Scallywag developed a problem with its foresail.

As its rivals took advantage, the crew of Scallywag were forced to take the boat away from the racing line and go the wrong way for several minutes to give themselves room to bring down the sail and work on it.

"Shortly after the heads the yacht had an issue with the J2 foresail tack fitting. The team got the sail down safely & storm jib up while they work to repair it," Scallywag's social media account tweeted.

The storm jib, designed to be used in much higher winds, is a lot smaller than the normal foresail - as a result, Scallywag's speed slowed down and it lost ground on its rivals.

LawConnect took over to establish a lead it would not relinquish for the rest of the afternoon.