I've found a transcript of a baptism of a Miles Ismay s/o Miles bapt in Newcastle -u-T on 09 Mar 1766. Could Miles jnr also have become a master mariner and predeceased his father?(He's got enough time to become one between 1766 and 1810) He may have been the one who died in 1810 and whose burial is mentioned in a book published in 1827 (two years before Miles snr died).
The will dated 1810 was written by Miles snr and does not mention Miles jnr.. Why not? Because he had just died and that precipitated a new will to be written. On the link on the first post it also says a codicil was added in 1813, so it cannot have been proved / proven in 1810.
Regarding the transcription of the 1766, baptism of Miles Ismay at Newcastle upon Tyne, in the reply by LizzieL.
On f m p there is also a transcription of a 1763 Marriage at Newcastle upon Tyne for:-
1763, 23rd May
Miles Ismay = Elizabeth Lowrey
One 1763 transcription for spouse Elizabeth has a note 'prev married'
Boyd's Marriage Index (from a Transcription)
1763
Newcastle All Saints, Northumberland
Miles Ismay = Elz Lowry
Mark