I recently went back to the Newsletter Index and searched for references to 'M'Ilh...'. It brought up six more items of Port News ten years earlier than the shipwreck, between August 1786 and July 1787, all concerning a ship called Mary whose master was McIlhago. Was this Robert, with his surname spelled slightly differently? Fortunately one report, that for 25-29 May 1787 (p.2) included the ship's master's Christian name, James. The ship Mary was a cargo boat carrying a variety of goods, including salt, cork wood, fruit, salmon and linen cloth.
I have for some time believed that James McIlhago who in 1765 was involved in founding a library in the USA (see my blog of 7 Feb 2009) must have been a sea captain, and surely now we have found that indeed he was. He must have returned from the USA to Irvine, Ayrshire and taken over the 'Mary'. The name of the ship might well indicate that either his mother or his wife's name was Mary, though I have to say that we have no proof that he ever married. My belief is that he was an uncle of the Robert who drowned in 1797.