Only 13 episodes exist.
From The Lost Media Wiki
According to an archive of DIC's old website, ONLY 13 episodes of Hammerman were produced. As all of the other shows listed on their site have the correct episode counts, I don't see why this would be incorrect.
Link - https://web.archive.org/web/20030402134126/http://www.dicentertainment.com/dic_shows.html#AShows