Tracking down the former owners of a boat you own, especially if the boat is more than 50 years old (mine is now 80!) accomplishes two key stewardship goals - the preservation of historic documentation and the prudent recording of repairs for maintenance.
A third, more FUN goal, (in my case, what turned into an international quest, and book) is the profound discovery of human connections and the illumination of history that occurs while doing the research. Think "Roots" and Ancestry.com for boats. While the people you meet may not be family by blood, they (or their children, grandchildren, or great-grandchildren) become family, in that bigger world community way, through a shared love for the boat or through the challenges faced while owning it.
Research starts with the documentation received at purchase - the legal documents of registration - and anything the prior owner passed along like Logbooks, maintenance records, etc. If the boat has a pedigree from one of the national or internationally recognized designers or building yards, it's likely there will be plaques, photographs, and even books about the boat or her sisterships.
In my case, there was nothing but the minimum information required for registration and the name of the owner I bought her from. The rest was a mystery. What I did next, then next, then next was the 7-year quest to British Columbia, California, and Denmark (four times!) that became the book, FINDING PAX.
While most people buy boats for voyaging and some for the challenge of the build, my boat took me places I never imagined, into history I never knew.