He was given command of HMS Exeter in November 1746 and was sent to the East Indies to serve under Rear-Admiral Thomas Griffin and Admiral Edward Boscawen.

Despite Powlett's evasions, he was court-martialled on 1 September 1752, but was acquitted due to Griffin's charges having failed for lack of evidence.

Powlett's rapid rise to a captaincy and his willingness to commence court martial proceedings against his superiors were a result of his family connections.

Even after leaving the Admiralty, the Bolton political connections remained sufficiently strong to ensure his continued promotion.

However, he had apparently already become a figure of satire and is believed to have inspired the character of "Captain Whiffle" in Smollett's 1748 novel The Adventures of Roderick Random.

He was appointed to command HMS Barfleur on 4 February 1755 and petitioned the Duke of Newcastle, then prime minister, for promotion to flag rank, on the strength of his family's support of the government.

While waiting at the rendezvous on 25 August, the ship's carpenter reported Barfleur's sternpost to be dangerously loose, and Powlett returned to Spithead for repairs.

In 1778 he went into opposition to the government over its handling of the American War of Independence, and joined Vice-Admiral Bristol in opposing the court-martial of Admiral Keppel.