Where did he say it was free? Your making a lot of assumptions about a boat you haven't even seen in a picture yet. What makes you think the interior needs replacing & the motor /drive a $1k of work?
Yes, assumptions are being made, but that is what experience leads to based on statements that are made.
First Clue: 1987. 30 year old boat that was built to last 15, maybe 20 years. Let's face it, Late 80s glass boats are not regarded for their impeccable craftsmanship.
Second Clue: Previous owner had to get rid of it ASAP. No one has to get rid of a working boat immediately. People have to get rid of projects that take up space, not working vessels. My assumption, based on previous experience, is that people know they have a dud, try to get as much as possible for it, and when other offers don't come on, they sell it to previously interested buyers.
Third clue: Jumped in and started cleaning. Indicates a dirty boat. Dirty boats are neglected boats. 30 year old dirty boats are problems.
Fourth clue: The floor needs to be repaired. Indicates rotting, worn carpet, bad or warped wood on the deck. Experience tells us that boats rot from the bottom up. If the floor is bad, there is a very high probability that whatever the floor attaches to is bad as well. If the floor is failing, water gets through to the foam. As soon as the foam is soaked, all bets are off.
Read through the restoration forum. It is full of people that started with a small floor repair that ballooned into an entire rebuild. We are not trying to discourage anything, but trying to educate what to look for here and what to expect, based on experience. The OP needs to get the big picture of what it is going to take to fix this boat BEFORE he begins, not during. It is very easy to get caught up in the adrenaline of buying a boat. Buyers are flying high and looking at the boat through rose colored glasses, especially when they get it for a "steal". It is easy to justify defects as small and worth it because of how cheap the boat was. We are trying to shed some light on the big picture here.