Upgrade 9.5hp Johnson to Chrysler 20hp- Thoughts??

So I have an older 14' Sea King V hull with a 1964 9.5 Johnson (put new impeller, and carb rebuild into last year) that just won't get it on plane. I found a Chrysler Sea King 20hp on craigslist today for $495 (is this a fair price?)and I'm going to look at it tomorrow. The guy says he's an outboard mechanic, that it's a low hour unit and it runs great. He's going run it for me in a test tank. I know these motors are harder to find parts for but I'll deal with that when the time comes. What are everyone's thoughts?? Is it worth the cash for the upgrade??

In my opinion NO. WAIT to find a evinrude/johnson 25hp for the $500 that guy is asking for his sea king. I have had 2 9,9hp and 1 15hp sea king/chryslers(still have the 15). all have run fine and have been good motors but replacement parts can be a challenge to find. $500 will get you a evinrude 25hp if you are patient.

Id wait. Chrysler's are junk IMO

OK, Thanks guys. I think I'm going to try a different prop on my johnson and see what kind of results I get