I have a 27' Sea Skiff, 1960, with the original 283 still in it. I've also restored and repaired quite a few as well.
There are a host of areas that will need carefully, knowledgeable inspection, before you purchase. If the guy doesn't know Sea Skiffs, then call someone else.
The wise choice is to have the boat surveyed by a qualified and familiar specialist. You can look over the boat all you want, but it takes years of experience to sort through all the likely places that issues tend to hide. If it was here, I'd know precisely the first places I'd look, if for no other reason then to save myself the bother of crawling around in the bilge looking for other stuff.
Last word of advise, do not even believe what the owner, former owner or any of his friends or cohorts say about the boat. First off, they probably don't have a clue what they're talking about and most importantly, they're trying to sell the boat, so they just naturally going to lie about it. Some more things, don't let anyone tell you it doesn't have rot, it does. I don't care if it was museum kept for the last 40 years, it's got rot in it. If it has a 'glass sheathing on it, turn and run in the other direction as quick as you can.