The Lord Clive was sunk in 1762 following a naval battle with the Spanish, as her maverick captain Robert McNamara tried to retake the city of Colonia del Sacramento.
About 272 sailors went down with the ship, while the 78 who made it to shore were quickly tried and executed by hanging.
Ruben Collado, who found the wreck in 2004 and now intends to raise her, says there is a fortune in gold aboard.
The riches had been sent by the East India Company – the all-powerful global corporation of its day – to pay men fighting to conquer the continent as part of the Seven Years’ War.
Collado said the ship was as important for cultural reasons as for the wealth on board.
“If that ship had not failed in its attempt to retake the city of Colonia del Sacramento, today we could be speaking English throughout Latin America,” he told the Times newspaper.
“Had the Lord Clive fired its cannons from a greater distance, Colonia del Sacramento would have been destroyed in one hour.
“The rescue of the ship would have an impact on the city no less important than when UNESCO declared it — justly — a World Heritage Site. This is the history of Latin America and the Spanish.”
Collado would be entitled to half the booty if the operation, which has been approved by the Uruguayan government, is a success. Raising the ship is expected to cost £4 million and take a team of around 80 people.