Massachusetts Soldiers and Sailors in the War of the Revolution, 17 Vols.
Hacker, Hoysteed. Petition dated Boston, July 30, 1781, signed by Job Prince, Jr., in behalf of John and Andrew Cabot, of Beverly, asking that said Hacker be commissioned as commander of the ship ‘Buccanier’ (privateer); age, 36 yrs.; stature, 5 ft. 11 in.; complexion, dark;
The New York Weekly Museum
Hacker, Capt. Hoysted, an old revolutionary officer, died, aged 69 (Dec 14th, 1814)
This pins down his birth year as 1745, and his age in 1794 when his first wife died, at 49 years old. This would be when he would start looking for another wife, considering his son Hoisted was a newborn infant.
My theory on the age of his second wife Mary Jacocks is that she was no more than ten years younger than him which would put her birth date at 1745-1755 or so range. Of course this is only speculation, and perhaps she was much younger, but this seems unlikely.
Is there a Mary Jacocks in that date range in your research?