Merganser was laid down as YMS-417 by Stadium Yacht Basin of Cleveland, Ohio on 9 January 1944; launched 29 June 1944; and commissioned 11 November 1944.

Arriving in Hawaiian waters in October, she was assigned to the Philippine Sea Frontier and continued her voyage, reporting to ComPhilSeaFron in January 1946.

Before leaving the area in mid 1954, she served several tours as observer for Armistice violations off the west coast of Korea.

With the designation MHC-47 effective 7 February 1955, Merganser conducted underwater sound tests at Carr Inlet Acoustics Range in Washington for the first 2 weeks in April and then got underway for duty with the 11th Naval District at San Diego, California.

There, until February 1958, she provided target towing and sonar training services, conducted harbor defense exercises, and performed search and rescue missions.