I have just a few more observations about this ancestor. First of all, I am certain he is, in fact, an ancestor of mine as his arrival in America and subsequent line is well documented. His grandson, William McCoy (1750-1835), was a Revolutionary War veteran and eventually moved to Pike County, Kentucky where he was granted a parcel of land. He is thought to be the ancestor of all 'McCoys' in Eastern Kentucky and was my 5th great-grandfather. I grew up in Martin County, Kentucky a former territory of Pike County.
Another observation concerning John McCoy is that he was a 'Jacobite' and initially left Scotland because of a failed rebellion to reinstall King James II on the throne. I am curious about this because the MacKay clan was notoriously anti-Jacobite so John must have gone against clan policy in supporting the former king. So, did he leave Scotland for fear of retaliation from the current government or did he flee because of possible clan retribution? I would love to know more.