This may be your man.

George Martin

Dean W. Tainter

Residence Charlestown MA; a 25 year-old Bookkeeper.
Enlisted on 7/20/1861 as a Private.
On 7/20/1861 he mustered into "A" Co. MA 13th Infantry [USA]
He was discharged for promotion on 5/28/1862
On 5/28/1862 he was commissioned into US Navy
(date and method of discharge not given)
Other Information:
born in Boston, MA

Sources used by Historical Data Systems, Inc.:

- Massachusetts Soldiers, Sailors and Marines in the Civil War
- The Story of the 13th Massachusetts Volunteers
(c) Historical Data Systems, Inc.