He has two sets of incomplete records one dated 8/Jan/1938 issued at the Merchant Navy office Galway. There is no mention of any ships or rank, just saying he lost his discharge book in 1930.
The second record dated 16/May/1930 issued at Glasgow gives him aboard the vessel ARETHUSA? official number 121316 (you would need to check it out as the writting is not very good.) after previouly being discharged, no doubt due to his shrapnel wounds. His rank is given as Fireman Trimmer?
If indeed this is the correct ship you would need to consult her 1930 crew agreements which should be available from here. Search via official number.
http://www.mun.ca/mha/holdings/viewcombinedcrews.php?Official_No=121316fortunately her logbooks for the period seem to have survived.
Although the second record gives information that he was previously discharged. There may be info in the crew agreements and logbooks that will give the name of his previous ship, if indeed he had one after being discharged. What they will tell you is his home address and NOK.
The personal records of merchant seamen covering the period of the first World War have been destroyed.