Good suggestions, but unrelated witnesses - in this place, at this time - are much less common than related ones. Also I've done a lot of work on Poole families and I'm reasonably familiar with the names of the regular witnesses there.
But the main point is that the fishing / seafaring / piloting families in Poole had so many interconnections* that it seems far more likely to me that there is a connection somewhere and I just haven't found it yet.
*For example Mary Boynes died in 1829 and in 1830 the widowed John King married Martha née Jenkins, widow of James Tilsed - James being brother to the John, Mary and Aphra mentioned in my post. And in 1836 Martha's son by James Tilsed, also James Tilsed, married Sarah Stone, daughter of Susannah Boynes - who was sister to the Eliza and Mary mentioned in my post.
(To clarify - I don't believe these connections are relevant here, just examples of how tightly woven these families were.)