YIKES.... retail value on this boat is like 3600 bucks. Usually book value is more then you should pay. Is it not the case with seadoo boats?
My wife would laugh if she heard me say this, as I sometimes don't follow this advice myself... but it sounds to me like you are trying to sell US the boat. You are so excited, and I don't blame you a bit, but could it also be clouding your judgement? Well, when I've gotten that excited in the past it has clouded my judgement.
I suggest that you take a deep breath or two and:
-find someone who knows SD boats who can look at it with you
-or better yet, have it checked out at a SD dealer
-remember that EVERY spring LOTS of folks pull the tarps off of their boats and put them up for sale. It isn't the end of the world if you miss this one
-Double your search efforts. Nothing seems to help to take the pressure off of an impulse buy like having multiple options... so you don't feel overly pressured to jump on one before doing the proper leg work.
-don't read too much into his display of distress over a little scratch. Over-reacting to an obviously minor flaw is one of the oldest sales tricks in the book, and people use it because it works. Nothing like re-focusing a prospective buyer on something trivial as a means of distracting them from the legit issue(s) that might be spotted if looked at closely. Not remotely saying that IS what the guy is doing, as I don't know him. Just that i bought a classic Corvette a few years ago from a guy that seemed exactly like you described... meticulous, with a couple of pristine classic cars in the spotless garage. He went on and on about the 1" long scratch in the front bumper and how he cried when it happened. I believed him and took it as evidence of how anal he had been about maintaining the car. Little did I now there were SERIOUS safety issues with the car that would cost me another $4,500 and have it in the shop for the next month and a half. And don't even get me started on that Sexy Jaguar I bought because it was such an awesome deal and I was afraid someone might beat me to it... and sent back to the shop once a month on a flatbed to have expensive stuff fixed.
You might buy some time to gather your thoughts by scheduling a test ride and then a trip to the SD dealer for pre-buy inspection (in that order! Else you'll be negotiating price with the adrenalin from the test ride driving you BUY NOW!... which is another clue that the guy is a sales pro, as he wants you to have cash in hand at the test ride). You'll have more info to make a logical decision and more time to keep looking for other options. If the guy really is as meticulous as he seems, then he should respect that you are too and be willing to work with you.
Good luck, bro!