Few, if any, of the laws that apply to new cars also apply to boats.
Things like window stickers with the MSRP are just not seen on new
boats. You also don't see the huge number of companies that make a
living from being "industry watchers" that you see in the auto
industry.

Even today, I suspect most new boat dealers are pretty small
operations, with fairly small profit margins. When I was in the boat
business 20 years ago, we could usually buy a new boat in the $100K
range for maybe 20% off list price. Even if we could sell if for
list--which was rare--that's not much of a profit margin. Out of that
we had to pay all our costs, especially the "flooring" costs--interest
on the money we had to borrow in order to actually buy a boat and bring
it into inventory. Needless to say, if we didn't sell a boat pretty
quickly, we lost money on it! We tended to keep just a few in
inventory, and take orders for most of them.

That model may be different for the really big boat companies and their
dealers, but for the smaller companies I suspect it hasn't changed
much.

Bottom line, I suspect if you can get a new boat for 10% off list, you
are probably doing pretty well.