A 28-foot Formula speedboat caught fire south of Gardiner's Island, near Cartwright Island, according to Coast Guard Petty Officer Steve Strohmaier. Ed Michels, the East Hampton Town harbormaster, said the boat was near Buoy 12, in the south channel.
A passer-by told marine officials the engine caught fire, but the Coast Guard had not yet determined the cause.
People on Jet Skis picked up the boaters and took them to shore, the Coast Guard said. No injuries were reported.
Shelter Island Fire Department volunteers helped extinguish the fire from a department boat.