The missing men, all experienced sailors, ran into trouble as they were returning to Britain from a sailing event in Antigua in the Caribbean. They had reported that their vessel, the Cheeki Rafiki, was taking on water, forcing them to change course for the Azores.
On Friday (local time), a Navy search crew discovered the overturned vessel about 1,000 miles (1,600 km) off the Massachusetts coast, but they detected no sign of the crew, the US Coast Guard said in a statement.
A Navy swimmer reached the 40-foot (12-meter) yacht, finding its cabin flooded and windows shattered. The swimmer knocked on the hull but heard no response, the statement said.
"The ability to locate that overturned hull, but still not be able to find a life raft is indicative of how unlikely it is that the life raft is still out there," said Lieutenant Joe Klinker, a spokesman for the Coast Guard's 1st District, which oversees Massachusetts waters.
Klinker said the search would be called off by midnight Friday if there were no further developments to indicate the missing sailors might still be found alive.
US authorities originally abandoned a search for the ill-fated crew 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 over 200,000 people
