Yes, there is. The better data providers are available to subscribers. Most brokers and surveyors have access to this information. As far as the non-subscriber, there are some web sites that offer some data but I would not trust it. You can search the sales ads and get a close idea what most most owners think their boat is worth. Sadly, no public data to what the boats actually sold for. That's where the brokers come in. Hope this helps
I thought NADA did boats. Not motor yachts mind you. Sold Boats is the broker accessed arm of YachtWorld as far as I know. One could ask a broker for recent Sold Boat comps I guess. There may be an issue here. YachtWorld listings are able to be entered into SoldBoats after the sale. The selling price is simply listed by the broker(s) involved. It seems to be the honor system. It is information and most of it will likely reflect actual final selling price, but who knows? I have only peripheral knowledge of this as a friend of brokers. Is this what you are thinking about Cliff?
NADA does yachts. As far as I know, only marine lenders and some surveyors might use this source. The primary source for sold boat prices is YachtWorld; the sold boats link is available only to subscribers which is primarily brokers and surveyors. Gr8trn is correct that the price is entered by the listing broker (or staff) and relies on the honor system. My personal opinion is that there are several manufacturers who keep their prices elevated because (1) they do not post the actual selling price and (2) lack of cooperation with outside brokers means that the real prices don't get posted. It used to be, pre-COVID, that if the selling price was the same as the ask price, then you knew the actual selling price was being withheld. Now that the "selling for ask price only" movement seems to have dissipated, then perhaps we can at least rely on the cue that ask price and sell price rarely equivocate.
I have checked Nada's boat prices several times in the past for trailerable outboard boats. Just looked at a couple of 50' diesel SF's and they were in line with current prices on YachtWorld after adding the equipment listed to get a more accurate value.
BUCValu seems to have pretty accurate pricing for anything non-custom. I know some lenders and insurance companies use their valuations. They are subscription based but reasonably priced.