A man was taken to hospital after a boat exploded into flames next to a Lake Macquarie yacht club, blanketing the skies in thick black smoke, north of Sydney today.

Around 1.10pm, police were called to the Lake Macquarie Yacht Club on Ada Street, Belmont following reports the moored vessel had caught fire.

Up to 40 Fire and Rescue NSW officers attended the scene to extinguish the blaze.

A boat exploded into flames today next to the Lake Macquarie Yacht Club, north of Sydney. Picture: Supplied. (Supplied)

Witness Andrew Cooke told 9NEWS he saw the fireball erupt from the boat before a man onboard jumped off the vessel.

"I heard a big bang and a fireball came out the back of the cruiser," he said.

"Shortly after, the bloke inside jumped overboard."

Thick black smoke blanketed the sky over the club as emergency services worked to extinguish the blaze. Picture: Supplied. (Supplied)

The vessel's 59-year-old occupant was taken to hospital in a serious condition with burns to his face and hands. Picture: 9NEWS. (Supplied)

The 59-year-old occupant of the prized boat, who had been cleaning at the time of the explosion, suffered burns to his face and hands.

He was treated on the scene by paramedics before being taken to John Hunter Hospital in a serious condition.

Inside the yacht club, people took cover as the boat caught fire before emergency authorities also evacuated around 100 people from the yacht club as a precaution.

Authorities are now investigating the cause of the inferno. Picture: 9NEWS. (9NEWS)

The boat's charred wreckage remains moored at the yacht club. Picture: 9NEWS. (9NEWS)

Inspector Mark Cavanagh from Fire and Rescue NSW said the club's staff worked efficiently to deal with the situation.

"Management of the club did a really good job getting people out quickly, with approximately 100 people evacuated from the club," he said.