The third ship to be so named by the U.S. Navy, Inca was a motor boat, built in 1917 and acquired by the Navy from her owner, F. B. McQuesten of Boston, Massachusetts. USS Inca, a 23-ton motor patrol boat, was one of a group of nine motor boats built by Herreshoff Manufacturing Company, Bristol, Rhode Island, in 1917 in the expectation that their private owners would make them available for First World War service.

She was acquired by the Navy in July 1917 and commissioned 28 July 1917 at Boston.

A versatile craft, Inca was first assigned to the First Naval District and patrolled outer Boston Harbor. She also performed coast convoy duties with submarines during this period, and acted as test ship for submarine signaling and detector devices.

She was reassigned to Fifth Naval District in October 1917 and arrived Hampton Roads, Virginia, 3 November. Inca's job was to serve as rescue ship for aircraft from the Naval Air Station on flights over the Chesapeake Bay and Potomac River.

She also served as a seaplane tender during 1918, and spent time on harbor patrol in Hampton Roads. Inca was assigned 26 July 1918 to the Industrial Department, Hampton Roads, as a dispatch boat, and remained on this duty for the rest of her time in Navy service. Inca lost her name in 1918 and was thereafter called simply USS SP-1212.

Inca was returned to her owner on 17 April 1919 after the end of the wartime emergency.

• This article incorporates text from the public domain Dictionary of American Naval Fighting Ships. The entry can be found here.
• USS Inca (SP-1212), 1917-1919. Later renamed SP-1212