you can always tell its a scam when the seller wants you to contact him before bidding. howver this one seems a bit different. have the scammers become a bit smarter and changed the way they list it. for one the price is not a ridiculous.
I would contact them and ask for a phone number. Get details about the transaction and then you'll know if its a scam. If they won't take a cashiers check or don't have the papers, then its a scam. I bought my boat on ebay and was very worried it was a scam. I did all my homework to verify ownership and legality and got a great deal.
Watch out on ebay for this sort of thing. I was almost scammed a few weeks ago. Someone had a boat for a great price but wanted all questions sent to a different email. So I sent one to that address first and didn't hear back so I went through ebay and asked the seller a question and he told me someone hacked into his account and posted the boat for sale and that he had never owned that boat so he pulled it off, then the next day the other guy i emailed first said the boat was still for sale and it was in texas instead of louisiana and that I could still buy it if I wanted to. So needless to say I was disappointed in what I thought I had found. So watch out on Ebay.