In 1750 he married his cousin Susannah Taverner, another daughter of William Taverner. (Masters had married her sister, Sarah - see above) and built up a business in the cod trade in Trinity, as well as building ships there. In 1776 he built a large brick house there with bricks he imported from Dorset that is the oldest brick-built house in North America. It was recently restored by the effort of a Poole-based Trust.
Benjamin's elder brother Isaac remained in Poole to conduct the business and built a mansion in Thames Street that is now the Mansion House Dining Club and Hotel where the symbol of the family's wealth, a pair of dried cod, are depicted in marble on a fireplace.
Benjamin surrendered Trinity to the French in 1762 and thus avoided damage to his own fishing premises as well as those of other Poole merchants. His business rapidly expanded to other ports and to Labrador. His brother Isaac died and Benjamin returned to Poole in 1776.
He used the influence his brother had built up to become Mayor in 1779 and became the leading spokesman for the Poole merchants, urging measures to bar the Americans from the Newfoundland trade. His own trade amounted to the largest share of any - 7% of all the fish shipped to Europe in 1789. By 1793 he had a fleet of 30 ships. His business survived the French revolution and depressed markets in Spain and Italy. By 1800 he was assessed in Poole at £3,000 value in exports and imports, by far the largest of any Poole merchant.
He served as MP between 1790 and 1796, and his views, powerfully expressed, reflected many West Country merchants advising the Houses of Commons and Lords that the merchants knew better than government how to manage the island's affairs and wished to be as free as possible from interference with the conduct of their business.
His Diaries are lodged with the Dorset Local History Centre at Dorchester, containing many details of Poole life and national and local politics of the age. "Mansions and Merchants of Poole and Dorset" (Poole Historical Trust - now out of print) contains a detailed account.
Benjamin died in 1802 and his business interests passed to his son-in law George Garland, who been Mayor in 1788 and was to serve a second time in 1810.