David Halpin, 62, hoped to sail on a mercy mission with 17 tonnes of aid aboard a Brixham trawler earlier this month.
But Maritime and Coastguard Agency regulations ruled out the use of the 80 foot (24.2 metre) craft.
Now he has chartered the 200 foot (61-metre) long Danish-based cargo vessel, the Barbara, which can carry up to 1,000 tonnes.
He is one of four people planning to start the 3,000-mile voyage from Beacon Quay, Torquay, on 31 January.
The total cost of the vessel and aid will be about £100,000.
Mr Halpin has been in contact with the Medical Aid for Palestine organisation in London to establish what supplies were needed.
The aid is intended to help the 1.1 million Palestinian refugees from Israel who live in Gaza.
Mr Halpin, who worked at hospitals in Torquay and Exeter, said: "We hope it is the first of many such voyages.
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This voyage is a chance to make a difference
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David Halpin
"Because we have now got more cargo space we are hoping to take up to 100 tonnes of food, clothing and medical supplies."
Mr Halpin is putting forward a lot of the money to fund the voyage himself.
He said: "The only way I could succeed in this was to commit my own money and hope people will come on board later."
He has asked the Foreign Office to clear the vessel's entry into the Israeli port of Ashdod, north of the Gaza Strip, and for road passage through a checkpoint into Gaza.
Mr Halpin, whose party will fly home after the aid mission, said the voyage was "a chance to make a difference".