[3] In 1780, on board la Couronne, commanded by Guichen, Marchainville participated in battles of the American Revolutionary War and bore himself so well that his captain mentioned him favourably in dispatches.
On l'Aigrette, commanded by Fleuriot de Langle he functioned as an "officier chargé du détail", as he also did on board the la Résolue.
Leaving Newport, Rhode Island for île de France in consort with le Réfléchi, la Fauvette was separated by a sudden storm in the approaches to the a great bank off Newfoundland and so Marchainville returned with only one ship, despite bad weather on the return voyage.
A good and brave sailor, he was also noted for his scientific researches, which won him a "lunette de mer" on 23 August 1777.
He and his brother Ange died on the La Pérouse expedition, and their father (the wealthy court banker Jean-Joseph de Laborde) erected a blue-turquoise marble rostral column beside a pool at his château de Méréville, decorated with 4 ships' bows, to glorify their virtues.