A. I'm confused. What do civil forfeiture laws have to do with being pulled over and not being able to own your boat? The way that I've always gone about dealing with someone, and I much prefer dealing with a dealership or business because of reasons like this, is that you agree on a price and come up with a bill of sale. Add everything to the bill of sale like the hull number, serial number on the engine, VIN on the trailer if there is one and so forth. Once you have a bill of sale, you have a binding contract, so if he were to not want to give over the title's or so forth then you'd be able to take him to court or take him to small claims court. An annoyance for sure, but definitely a possibility when purchasing anything nowadays.
B. There's a multitude of reasons why he probably wanted you to pay him with cash including... it's instant, you don't have to wait for a cashier's check to clear, people will oftentimes change up the sales price with regards to taxes paid - not condoning this, you don't have to wait for a credit union to approve you and it's much quicker and easier. I wouldn't have any issue at all paying someone cash for something and isn't really a red flag imo. If it was something like a house where it was hundreds of thousands of dollars then I'd be a little bit more hesitant or skeptical.
C. I understand where the seller is coming from to be completely honest, and no offense, but I never talk about a price over the phone or via email on a boat I've never even seen before. The same goes with something that I'm selling and someone is trying to get me to agree on a price over the phone with something they've never seen, or especially when they lowball you. That's a huge red flag to me that they're a tire kicker or aren't serious about buying the boat, or whatever it is that I'm selling, and especially if they live locally. If they lived 400-500 miles away or more and said "Hey if I come out, like the boat and want to buy it then are you open to offers or are you set on the price?" Or "Hey if I come out, like the boat and want to buy it then can we come up with an agreed upon price over the phone?" That way it shows the seller that you're interested, ready to come out and look at it and so forth. I sold my last boat in September of 2020 and it was such a PITA dealing with tire kickers on Craigslist that I almost pulled the ad because I didn't want to have to deal with people wasting my time and making lowball offers. So, I can definitely see where the seller is coming from in your instance, and the only time I've ever come to an agreed upon price over the phone with a boat sight unseen was for an out of state purchase. But even at that point, I'd still told the seller that I was interested in the boat and looking to have a surveyor come out and inspect it, so it would be an offer pending a favorable survey.
D. Why don't you post an ad in the "For Sale/Wanted" section of the forum and let people know what you're looking for? You say you're looking for a GW 190 Tournament that "I could afford" and "Appeared to be in the condition that I wanted". That's extremely vague as it doesn't say at all the range of years that you're looking for in a boat, nor does it say what your price range is. I just spent the last year looking for a 228 Seafarer and would say something like I'm looking for a 1998 and newer Grady White 228 Seafarer, preferably with 4 stroke power, a hard top and a trailer, and my budget is a max of $35k. That way, if someone on here has a boat they're looking at selling then they could respond to your post or send you a direct message or lot of people are bored and want to "help" other people spend their money. So they'll look for boats for sale for that person to try and help them out. I'm doing the same with another member on here that's looking for a GW 228 Seafarer similar to the one I purchased and have been talking back and forth by direct messaging.