"They hit the crew all over, on the head, everywhere," Ismail Abdurehman, the rescued captain, said.
The pirates also stole supplies and most of the belongings of the crew of the dhow Vishsakalyan.
Radios, television sets, phones and presents for relatives were taken, with only three chickens and the boat's cat remaining.
Abdurehman said that the crew had been carrying charcoal from Brava, in Somalia, to Sharjah, in the United Arab Emirates, and were unable to call for help when attacked because their assailants had broken their VHF radio antenna.
The pirates cast the sailors free while firing gunshots into the air and shouting "Go, go, go", Abdureham said.
Without supplies
The crew, from the state of Gujarat in India, was left without supplies and set off for Socotra, a Yemeni island, to get help.
However, Dario Precioso, a lieutenant on the NPR Corte-Real, the Portuguese warship that rescued the sailors, said that without provisions they "would probably have died if we hadn't found them".
The crew of the NPR Corte-Real provided food and fuel.
A rise in piracy in the Gulf of Aden has led to international navies patrolling the area's busy shipping lanes.
Despite these efforts, the International Maritime Bureau has said that more ships have been attacked off Somalia in the first six months of 2009, than in all of last year.