Are there service records for merchant marines, circa 1950?

Hi there! My great-grandfather's death certificate mentioned he was a Merchant Marine at his time of death, but that occupation never came up too much in family discussions, except to say he was a cook, I believe, on a ship. He died at the US Marine Hospital in Chicago (4141 Clarendon Ave) in 1950, and I am trying to locate any records that might exist about him. Can anyone point me in the right direction? I have no further info to offer, except that his death cert did confirm a position as a galley helper. Thank you in advance!