Generally boats, motors, and trailers, are marked up 32%. A lot of dealers are on a floor plan which means they borrow money to buy product and then pay interest on their inventory. Some pay monthly, other payments differ. Best time to buy new is at a boat show during the winter months. Dealers are scraping by because no one wants to buy a boat when they can't use the until spring.
Have your finances in order before purchasing, in other words get an okay from your bank, credit union, etc on a loan and have the process in the works or walk in with cash. Many people think by walking in with cash impresses the dealers, other than getting paid today instead of tomorrow with the loan draft, cash doesn't sway them because they get paid before the product leaves the dealership.
A decent offer is around 15% below list price and little if anything on a sale price. When talking prices and features, do your product homework beforehand then so you can make up your mind if buying this brand is better, or no so good, to other brands you have looked at.
Make sure the dealer will show you the operation of the motor/boat and have them start the motor to show you how before taking it home.