Ya, go take a look at it.
My thoughts are to not bring any cash with you, and not even the checkbook; no impulse buys. That way you can look at the boat clearly, what would need to be done. Obviously an engine change out, but what else would you want to do?? Go ahead and tell the seller your story. And then take a night to think about it and make a reasonable offer if it makes anywhere near sense. Someone else in your extended family may end up with it this way, this gives you control; I'm sure there were piles of kids in that boat at times.
I collect antiques as a hobby (quarter sawn oak furniture 1910 -30"s mostly) and am shocked by what other family members let go sometimes. Most people want new things in life, there is not many like us that cherish past generations coveted belongings. But something must have struck a chord with you and with 1635 posts to date, I'd say you're into it.
Go, take a look at it; bring no money if it is something you really want. That technique works for me.
Best of Luck.
David