Last I checked, the filing fee for a lawsuit in Florida was $295, and you can't sue for title in small claims court. That's before the cost of serving your lawsuit on the original owner, whose address you don't even know, or motion fees and costs associated with obtaining permission for substituted service. And yes, there's no guarantee that you'll win - the original owner could claim that he never sold or gave away the boat and that he wants it back.

It was childish of you to attack jk for pointing out that your most logical remedy is to seek a refund, given that you've described this as a $100 boat.