However, she made one voyage as a slave ship in the triangular trade in enslaved people, and two as a whaler in the British southern whale fishery.

[5] The ship arrivals and departures (SAD) data in Lloyd's List (LL) showed her with Francis, master, making a voyage to Dominica, via New York, in 1787.

Furthermore, in 1789 LL reported on 6 February 1789 that Duchess of Portland, Francis, master, had put into Dartmouth in great distress.

LR for 1792 showed Duchess of Portland with E. Lamb, master, Hamilton, owner, and trade London–Jamaica, changing to London–Africa.

[9][a] LR for 1794 showed her master changing from E. Lamb to Pollock and her trade from London–Africa to London-"Grdlp".

The 1798 volume showed her master changing from Pollock to J.Smith, her owner from Park to Mangles, and her trade from London–West Indies to London–Jamaica.

Duchess of Portland, Cleveland, master, was reported "all well" on 9 December off the coast of Brazil.

The Register of Shipping (RS) for 1806 showed Dutchess of Portland with Thompson as master, T&R Brown as owners, and her trade as London transport.

[16] Lloyd's List (LL) reported on 30 October 1812 that Commodore Rodger's squadron had captured and burnt Duchess of Portland, Thompson, master, as she was sailing from Newcastle.

[4] The Register of Shipping for 1813 showed Duchess of Portland with Thompson, master and owner, and trade Southampton–London.