Sailboat fire near the Savin Hill Yacht Club.

A 58-year-old man and his teenage son were working on their sailboat's motor in Dorchester Bay when it exploded around 5:10 p.m. Saturday, according to the Boston Fire Department.

The man suffered burns; boaters from the Savin Hill Yacht Club rushed out to the 15-foot boat, moored about 200 yards off shore, to rescue the two. The boat was located near the National Grid gas tanks.

Joseph Doolin, a South Boston resident, was driving down Morrissey Blvd. with his father down when he heard the explosion and saw a "white piece" went flying tens of feet up into the air.

"I had my windows up and I heard it," he said. "It was loud."

A Boston Fire Department boat worked to put out the fire under light rain ahead of the approaching storm.

The plume of black smoke was visible from the Fenway and Wollaston Beach in Quincy.

Kevin Haley of Mansfield was driving with his family and pulled over to watch BFD knock down the fire.

"You could see it down all 93," he said, referring to the highway.