My McGuirk family line goes back to Baltray, but while investigating McGuirks, I have come across dozens of merchant seamen from Baltray and Drogheda who are in ports on the west coast of England and Wales when the census is taken.
For example, in 1911 there is a ship called 'Colleen Bawne' in Collingwood Dock, Liverpool and also a tug called 'Warrior", both (from memory) I think entirely crewed by men born in County Louth. If you can't find your Louth merchant seamen at home on census night, don't just assume they're in mid-Atlantic as I once did.
As another example, there is a small craft at Neath, Glamorgan on the 1871 census for Wales. It's called the Erin and is so small it has a mate, not a master mariner in command. The mate is James Owens ,38,born Baltray, next two are Thomas Livis(?), 23, and Patrick King ,18, both born in Drogheda and the last is my ggfather (mistranscribed as McGuire). The writing is awful,
so I can understand the problem. I can only find this last one on FindMyPast .
If you've got a seaman somewhere in your line, it's worth a try.
Joney