The US Coast Guard said the hull had been discovered by the navy and a surface swimmer had identified the name on the back of the boat.
The Americans earlier said they would stop searching if nothing was found by midnight last night (5am GMT).
Experienced captain Andrew Bridge, 22, from Farnham in Surrey, and crew members James Male, 23, from Southampton, Steve Warren, 52, from Bridgwater, Somerset, and Paul Goslin, 56, from West Camel, Somerset, were on board the yacht which is thought to have sunk around 620 miles east of Cape Cod last Thursday.
The four yachtsmen were returning to Britain from a sailing event in Antigua in the Caribbean and reported that their vessel was taking on water, forcing them to change course for the Azores.
US authorities abandoned a search after two days due to treacherous conditions but resumed the hunt on Tuesday after a request from the British government and a public petition signed by more than 200,000 people.
More than 17,635 square miles have been searched in total.
Relatives had hoped that the men, all experienced sailors, had escaped the 40-foot yacht on a life raft after it started taking on water.