Super maxi Andoo Comanche overcame a challenging start in a dramatic opening to the Sydney to Hobart race to take the lead as the fleet benefits from favourable winds on Monday.

Six hours into the race Andoo Comanche was leading from LawConnect, Black Jack and Hamilton Island Wild Oats with the four super maxis all within close proximity along the south coast of New South Wales state helped along by northerly breezes.

The first retirement of the race came within two hours of the start with 40-foot two-handed boat Avalanche pulling out with a broken bowsprit reducing the fleet to 108 boats.

Several near collisions and line honours favourite Andoo Comanche and rival super maxi Hamilton Island Wild Oats making penalty turns inside the first half-hour made for a drama-filled start to the race.

Watched by a large spectator fleet, with tens of thousands more onlookers lining the shore of the picturesque Sydney Harbour, the action unfolded quickly just moments after the starting gun had sounded.

Andoo Comanche took a penalty turn inside the first few minutes after hitting a marker buoy. The boat was later seen flying a protest flag but the crew has not provided details of the incident.

Hamilton Island Wild Oats took their penalty turn shortly later but only after a debate between skipper Mark Richards and other senior crew members.

Despite the early drama on Monday, race organisers reported a clean start across all four lines of boats, which took place in warm sunshine after heavy early morning fog had hung over the harbor and limited visibility.

Weather forecasts indicate northeasterly winds for the early part of the race, providing the yachts with a comfortable voyage downwind off the states of New South Wales and Victoria. The faster yachts are likely to see that weather through to the finish line, but the rest of the fleet may have to contend with strong winds after the second day of racing.

The 628 nautical-mile race (1,170 kilometers, or about 720 miles) sails from Sydney down the south coast of New South Wales state and across Bass Strait to Hobart, the capital of the island state of Tasmania.

Black Jack, skippered by Mark Bradford, won last year, arriving at Constitution Dock in Hobart after two days, 12 hours, 37 minutes. Of the 88 boats that left Sydney, 36 were forced to retire due to dangerous waves and weather conditions.

Comanche set the race record in 2017, finishing in one day, nine hours, 15 minutes, 24 seconds. (AP)