1753-1813. He was the son of Vice-Admiral George Mackenzie, who flew his broad pennant as a commodore and commander-in-chief at Jamaica in the early 1770?s, and who commanded in the Downs in 1777. He died in 1780.
Mackenzie entered the service aboard the Montreal 32, Captain Phillips Cosby, serving in the Mediterranean from 1766-70. In 1771 he went out to Jamaica where his father was the commander-in-chief, and with this patronage behind him he was commissioned lieutenant and appointed to the sloop Tryal 10 on 5 March. A further nepotistic promotion followed on 15 April when he was elevated to the rank of commander, although he retained the Tryal until returning to England and being paid off in April 1772.
He next commanded the sloop Hunter 10, serving off the north coast of Ireland and Scotland, and later sailing for North America with despatches where he arrived the day after the Battle of Bunker?s Hill in June 1775. Upon returning to England he was then sent back to North America with a convoy bound for Quebec.
Once at Quebec, Mackenzie was seconded to lead a battalion of seamen ashore under the overall command of Captain John Hamilton of the Lizard 28. Whilst he was detained on this duty the Hunter was captured by two American privateers off Boston when under the temporary command of Lieutenant William Fooks on 23 November. Upon Hamilton?s return home in the following spring Mackenzie was posted captain of the Lizard with seniority from 12 June 1776. In the meantime Quebec had been relieved by Captain Sir Charles Douglas? small squadron on 6 May.
Commanding the Lizard, Mackenzie took the rebel privateer Putnam off New England on 4 December 1776, and after a refit at Plymouth in the spring of 1777 he went back out to North America. At the end of September 1778 he exchanged with Captain Hon. Charles Phipps into the Ariel 20, as his command was due to return to England. Success soon followed with his capture of the privateers New Broom 16 on 22 October and Resistance 16, however on 10 September 1779 the Ariel was caught by the French frigate Amazone 36 off the coast of Carolina and following a ninety minute action was obliged to strike, having lost four men killed and twenty wounded. Mackenzie remained as a prisoner aboard this vessel when the French fleet and American army tried unsuccessfully to dislodge the British from Savannah during the siege of September-October. He was eventually released at Cadiz and acquitted of blame for the loss of his vessel following his court martial at the end of the year.
Next appointed to commission the brand new Active 32, Mackenzie served in the Channel fleet during 1780 and in Commodore George Johnstone?s action with Commodore Pierre Andr? de Suffren at Porto Praya on 16 April 1781.On 1 July he captured the Dutch East Indiaman Heldwoltenmade after luring her in by the ruse of raising French colours, and with intelligence gained from her crew Johnstone was able to capture another four Dutchmen in Saldanha Bay three weeks later.
Proceeding to the East Indies, Mackenzie blockaded the rebel Tippoo Sahib?s Malabar ports and was in command of the seamen who reduced the Dutch fort at Negapatam. He then fell afoul of the commander-in-chief, Vice-Admiral Sir Edward Hughes, after the Active grounded on a coral reef when escorting a ship under the orders of the Calcutta Supreme Council, having been previously ordered by Hughes to attend the attack on Trincomale in January 1782. Towards the end of the year he removed from the Active and joined the Magnanime 64, and he was present when Hughes and Suffren met off Cuddalore for their fifth and final battle on 20 June 1783, losing one man and sixteen wounded. Returning to England with Captain Sir Richard King?s squadron, he went on half-pay in 1784.
From March 1791 through the Russian Armament Mackenzie briefly commanded the Culloden 74 in succession to the late Captain Henry Colins, paying her off in September.
Following the commencement of the French Revolutionary War in 1793 he was appointed to commission the Gibraltar 80 in May, but although he sailed with the Channel fleet at the beginning of its autumn cruise he parted company soon afterwards. At the Battle of the Glorious First of June in 1794 the Gibraltar lost two men killed and twelve wounded, and her long-range firing distracted Admiral Nielly’s Républicain 110 from a potentially lethal attack on Admiral Lord Howe’s flagship Queen Charlotte 100. However, Mackenzie’s failure to even attempt to break the enemy line, coupled with a wayward shot from the Gibraltar’s cannon that hit the British flagship and felled Captain Sir Andrew Snape Douglas, seemed to confirm the low level of intelligence many attributed to him.
He was never employed again but was promoted rear-admiral on 4 July 1794, vice admiral on 14 February 1799, and admiral on 23 April 1804. He died on 20 September 1813.
Mackenzie had a childless marriage with his wife, Elizabeth Chudleigh Mackenzie.
Following the Battle of the Glorious First of June one of his lieutenants wrote that Mackenzie was ?about the stupidest man possible?.