Monica, I don't know anything about the Merchant Marine, but I googled up this web site. You will see there they indicate, "www.usmm.org is NOT a government agency. We do not have your father's records. Read below how to get records for mariners and ships. We do have an extensive library with ship histories, information about sinkings, casualties, government documents and much, much, more."
They also list this resource:
Service Records of mariner killed during World War II:
Old Navy/Maritime Reference Archives I -Textual Services Branch National Archives and Records Administration 700 Pennsylvania Avenue NW Washington DC 20408