the 1776 marriage;
If the Ronans were a typical manx farming family with land then because the law fixed the descent to the eldest male child it would be unusual for the eldest to go as he would expect to inherit the land. Also any land possession would be noted - the lack of any will in the family would also suggest no land holding.
There was shipbuilding on the Island (tho this industry became more important early 19th C) but Liverpool was growing and many Manx moved there for work