What'd the guy lowball him at? $4200 still seems a bit high to me for whats out there, but if you like the float, go for it! I'd demand a water test drive for that price though. But I'm like Glenn, I'm a cheap bastard! Only two turnkey boats I ever bought were my Pickle (Stole that one, really), and my ( RIP ) Biesemeyer, and I paid far less than that for each of them.
http://phoenix.craigslist.org/nph/boa/1863201199.htmlNot a 460, but just an indication.
As far as the porpoising issues, I only know of two Sangers that had the issue. It's been an issue on MANY more, but various brands. These boats are old, spend most of their life on a trailer either outside or in a garage that is not climate controlled. Things settle in, and to be honest with you, I don't think any of the companies envisioned them still being used 40 years later. These are issues that CAN be dealt with through trim tabs, ride plates, wedges, etc, etc without flipping the boat and a total blueprint of the hull.
How many 70's and 80's cars are atill around, in the condition and every weekend use most of our boats are? Think about how many cars were made then compared to the number of jet boats, and it's kindof alarming!
Go look at it, do as Nordie says, jump up and down and see if you can break the floor. If it passes that, look at it under fluorescent lighting, if possible, to see if any repairs, bondo, etc exist under the paint. Then wet test it, buy it, and have a good time!
Ray