In doing my family tree on Ancestry.com, I have traced back to Isaac Beecher (1623-1690). Several trees and your information show that he was married to Mary Sperry (1624-1677). I have found that some trees have him married to another Mary Sperry (1650-1730 who was really married to a Mr. Peck). The US-New England marriages has a listing for Issac Beecher (died 1690, I found this listing a bit confusing) marrying a "Mary [Potter?]". Do you feel fairly confident that Isaac's wife was this Mary Sperry?
I just found your board here and found it really fascinating. Thanks!