I know from past ebay experience that I have a moral obligation to complete the transaction once I win the auction.
If you read the eBay fine print, it's actually a legal
obligation when placing a bid. A seller is not likely to go after you if you don't pay, but you can't guarantee that.
But if the boat is misrepresented I would have no qualms about backing out.
Defining "misrepresented" can be a challenge, though. The seller says it's in "good shape", but you call it "fair shape". Is that misrepresentation?
Most likely the listing will only describe the equipment on the boat. As long as it's all there, there wasn't misrepresentation. If there turn out to be defects, how can you guarantee the seller knew about them?
And, being an auction, everything is offered on an as-is basis unless specific guarantees are given. Which they probably won't be.
If you're serious about the boat, talk to the owner. If that checks out, send a surveyor to look and give you a report. Surveys turn up with serious problems all the time on boats that owners didn't know about. With that info you can make an intelligent bid.
unlikely a seller would let you survey after the auction is complete and then renege based on survey results. If that's what you want to do, better get the seller to agree before bidding.
I've bought two boats on eBay, and have been happy with the transactions. On both I did a thorough inspection myself before bidding -- surprisingly on one boat I was the only one of about 10 bidders to actually look at it.
Personally, I'd suggest that lots of boats sell through eBay. If you can't visit this one, there'll be others closer to you before long. Also, get some prices for shipping. It can be surprisingly expensive. A bargain far away may not be such a bargain by the time you get it home.