Elsewhere on the site you can read about the story of the fishing boat, the 'Iris' which was commanded by Donald Sinclair, an ancestor of mine. Though it goes into some detail, it doesn't mention the date on which the incident happened; it only states that it took place last century, by which it means the nineteenth.

I think it must have been before 1881, when Donald was about 75, but I'd be grateful if anyone could be more specific.