As a young man, he settled in Marblehead, Province of Massachusett Bay, eventually becoming the captain of a merchant vessel there.
[4] Through the end of 1775, Manley captured several additional prizes carrying cargoes of food, rum, coal, dry goods, all badly needed by the Continental forces.
In January 1776, for his "great vigilance and industry," Manley was appointed commodore of "George Washington's fleet", a group of small armed ships fitted out by him to harass the British and to seize supply vessels.
On June 7, Manley's ships encountered and defeated the 28-gun Royal Navy frigate HMS Fox in a brief engagement off the Grand Banks.
Upon his release, Manley entered privateer service to command Marlborough, Cumberland, and a prize, Jason,[8] until 1782, except for two more periods of imprisonment, one for two years in Mill Prison, England.
On a West Indies voyage, he made a spectacular escape from a superior naval force and, in January 1783, took the last significant prize of the war, Baille.