Westerly — A Stonington boat caught fire off Watch Hill early Friday, and five adults were pulled from the water by a good Samaritan, Petty Officer Jeff Thor of Coast Guard New London said.

All of those onboard were rescued within minutes and did not require medical attention, Thor said.

A distress call came at 7:15 a.m. from the 29-foot Dyer, at the same time that a Coast Guard boat from Southeast New England was out on an unrelated search out of Block Island, Thor said.

He said a good Samaritan nearby communicated with the Coast Guard by radio, then pulled people from the water within minutes and brought them to a dock at the Stonington Harbor Yacht Club.

All onboard — whose names were not released — had life jackets and did not require medical treatment, Thor said. One had tried to put out the fire, which began in the engine, by using three fire extinguishers, but was unsuccessful, Thor said.

After the fire was out, the boat sank, he said.

Capt. Jack Balint, owner of Fish Connection in Preston, was out on his boat with three clients on his charter fishing service.

He said he left Walker’s Dock in Stonington about 7 a.m. He said that he noticed the first smoke at about 7:10, by which time his boat was a few hundred yards out from the dock and nearing Sandy Point. He said he knew the boat had just started to burn around that time because otherwise he would have seen the smoke sooner from his marina.

“When a boat burns, it burns very, very black,” he said.

He said he rode over to see if he could help but saw the boat’s occupants were already riding on the boat of the good Samaritan.

Balint said he watched the boat for about 15 or 20 minutes. He said between 8:30 and 9 a.m. he noticed the boat burn down to the water and the anchor line melt.

Mystic Fire Department Deputy Chief Anthony P. Manfredi Jr. said the Coast Guard called the department at 7:21 a.m., and was at the scene with the Watch Hill Fire Department when the Mystic fire boat arrived.

“It was fully involved,” he said of the blaze.

Firefighters put out the fire within 3 or 4 minutes, Manfredi said.

Stillman Brown said he lives across the street from where the boat launched from a private dock about 6 a.m. He also watched its passengers return on a different vessel. They were brought to a nearby boat slip, he said.

He said the boat had only been there about two months and was being refurbished. “They were bringing it back meticulously,” he said. “It was really going to be a showpiece.”

Staff writer Tess Townsend contributed to this report.

d.straszheim@theday.com

Twitter: @DStraszheim