[1] On 18 September 1764 he was promoted to be lieutenant of the fifth-rate HMS Rainbow on the Virginia station, and remained in her till she paid off in October 1766.

[2] In March 1777 Williams commissioned the fifth-rate HMS Venus, in which he joined Lord Howe on the North America station, and was with the fleet off Rhode Island during their encounter with the French under the Comte d'Estaing on 10 August 1778.

[2] In April 1780 Williams commissioned HMS Flora, a new and large 36-gun fifth-rate, carrying 18-pounders on her main-deck, and an experimental addition of six 18-pounder carronades to her establishment.

Naval historian John Knox Laughton asserted that, "Such a decisive result ought to have given Williams full confidence in his novel armament, but it does not seem to have done so".

[2] In March 1781 the Flora was with the fleet under Vice-Admiral George Darby at the second relief of Gibraltar, and was afterwards sent on to Menorca, in company with the Captain Thomas Pakenham's 28-gun frigate HMS Crescent, in charge of some victuallers.

After a 2¼-hour battle (known as the Battle of Cape St Mary) the Flora captured the Castor (under Pieter Melvill van Carnbee), but the Briel had meantime compelled the Crescent to strike her flag; the Flora hastened to her consort's assistance, and the Briel made her escape.

The Crescent and Castor had been dismasted in the former engagement and were Jury rigged with only 300 unwounded men out of a full complement of 700 over the three ships.

His conduct was not blamed and was not even called in question; but Laughton opines that "when we consider that the Flora's broadside was nearly as heavy as those of the Friponne and Gloire together, it is impossible to avoid thinking that Williams did not understand the novel conditions in his favour".

The king desired that it should be retained by the family as "a memorial of the late admiral's long services and the high professional rank he had attained, and in proof of the estimation in which his character was held by his sovereign and brother officers".