[1] Serving in Gosport on the North American Station, Elphinstone saw action in the campaign that culminated in the removal of the French from Newfoundland at the Battle of Signal Hill in September.

In December, however, he obtained permission from his captain to leave Emerald in order to join his brother William's East India Company ship, Tryton, as third mate on a trip to China.

The two brothers' uncle, George Keith, 10th Earl Marischal, lent each £2,000 for the journey, which money allowed them to profit from the expedition.

In January 1781, when in command of the 50-gun HMS Warwick, he captured a Dutch 50-gun ship that had beaten off a British vessel of equal strength a few days before.

On 15 September 1782 in the Delaware Bay he led a squadron that captured the French 38 gun frigate Aigle during which Captain Latouche Tréville was taken prisoner.

[1] It was for a long time a thankless post, for St Vincent was at once half incapacitated by ill-health and very arbitrary, while Horatio Nelson, who considered that Keith's appointment was a personal slight to himself, was peevish and insubordinate.

It was however immediately afterwards lost in consequence of the Battle of Marengo, and the French made their re-entry so rapidly that the admiral had considerable difficulty in getting his ships out of the harbour.

On the renewal of the war in 1803 he was appointed Commander-in-Chief, North Sea (which at the time included Nore Command),[1][6] which post he held until 1807.

During his last two commands he was engaged first in overseeing the measures taken to meet a threatened invasion, and then in directing the movements of the numerous small squadrons and private ships employed on the coasts of Spain and Portugal, and in protecting trade.

He is also mentioned in passing in Robert Brightwell's novel Flashman and the Seawolf, based loosely on the exploits of Thomas Cochrane, 10th Earl of Dundonald (as is, in part, the character of Jack Aubrey).