How can I find this person? Genealogy qustion.

Looking for further ideas on how to locate an undocumented illegal irish immigrant in the New York area from 70 years ago.
What I have:
He would be a great Uncle of mine (Brother of my Grandfather).
Born in Ireland, raised in England
He was a sailor with the British Navy during WWI and afterward with the Merchant Marine.
I know of two ships he was on, the Matina (a British registry) in 1924 and again in 1925. and the S.S. Cold Harbor in 1926 which docked in Baltimore.
He does not appear on the 1930 Census.
Some time before 1940 he came to the US. No immigration records, probably jumped ship, but is on the 1940 Census where he is listed as working full time as a waiter in a restaurant. It gives the address in Mamaroneck, New York.
Around 1942 my Uncle visited while a Royal Navy Seaman, jumped ship and stayed for a few months where his uncle (the guy I am looking for) got him a job tending bar in a restaurant he was working at.
We won’t have access to the 1950 Census for another eight years.
He does not show up in any immigration or emigration papers that we have been able to find.
Nothing in the Social Security Index.
He is not listed in any of the grave listings available on line.
His brother died before he came to the US but he had a sister living in England as did his mother and father. We have had family members searching for some kind of correspondence to no avail.