Well, I guess everyone is different. But I see no downside to telling the seller you are going to take good care of the boat. They may not care like you but they might care like me. Either way it isn’t going to hurt anything.
Comodave,
I've had that technique work MANY times. Getting to know the seller IS a big part of negotiating. People do business with people they like and you want to be liked by your seller.
There's lots of ways to get into the sellers head, get him to understand your situation. You are selling yourself as a buyer to the seller.
I've had situations where the first contact was polite but the seller wouldn't budge a dime, so I always ask, "do you mind if I call again incase you've changed your mind... rarely do they say no.
I've also had sellers ask me how am I gonna take care of it. Yes, some are concerned how you'll take care of their past toy.
I've rarely purchased anything for asking, but there are exceptions. And at times I've gotten as much as 50% below asking, and quite often 25%. And, yes, there's a lot of buyers out there that overprice their boat because they think it's special, or they want all their money back they put in maintenance, fix up etc., which rarely happens.