It was to use the ships of the home government alone for its trade across seas.

It must not presume to manufacture for itself articles which merchants at home desired to sell.
England early strove to impress such trade regulations upon the American colonies, and succeeded in embarrassing and handicapping them seriously, although evasions of the navigation laws were notorious, and were winked at by the officers of the crown.

The restrictions were sufficiently burdensome, however, to make the ship-owners and sailors of 1770 among those most ready and eager for the revolt against the king.
The close of the Revolution found American shipping in a reasonably prosperous condition.

It is true that the peaceful vocation of the seamen had been interrupted, all access to British ports denied them, and their voyages to Continental markets had for six years been attended by the ever-present risk of capture and condemnation.

But on the other hand, the war had opened the way for privateering, and out of the ports of Massachusetts, Rhode Island and Connecticut the privateers swarmed like swallows from a chimney at dawn.