The men were stranded in four lifeboats and survived on water biscuits, raisins and the odd raw fish caught by hand.
They drank salty rain-water and tins of condensed milk they salvaged from the wreckage.
The newly discovered log tells of how the men were often drenched by heavy rain storms, leaving them cold and wet for days afterwards.
Three men died from hypothermia and exposure and had to be buried at sea during the ordeal in the middle of the Atlantic in February 1943.
Despite their plight, they managed to navigate their way using the stars and eventually found land at Antigua.