Continental frigates Hancock and Boston capturing

British frigate Fox, June 7, 1777

http://en.wikipedia.org/wiki/Continental_navy

Man Power was short in the Patriots Navy so African Americans were recruited. However, both sides signed African Americans into their navy. For the rebels the Africans had the ability to pilot the vessels and take responsibility of the ammunition on board the ships.

On the British side the Africans were much more willing and able to work. Mainly because the British soldiers were arrogant.

http://en.wikipedia.org/wiki/African_Americans_in_the_Revolutionary_War#African_American_Sailors