[Fr. Frank]

That speed seems pretty low. With my heavier 20' Seafari, running an re-manufactured '92 XR4 Mercury 150, I had a top speed of 53 with a light load, and 47-48 mph with an average load. And yes, that was with 3 heavy coats of Petitt "Trinidad" bottom paint. The difference was motor setup, tuning, and propeller selection.

Having once made a living in part by rigging and tuning high performance pleasure boats, I know the difference in performance between a well-rigged boat and a "default" dealer rigging job can be a 20-25% loss in optimum performance and economy. I made a lot of money off people who bought new boats from a dealer just by promising to deliver 10% more speed for an additional 10% of their purchase price. I never failed to deliver that 10%. Never.

Bottom line is that you should be getting 43-45 mph at a minimum, even with really rough bottom paint, and close to 50 mph with a smooth gel-coat bottom. (Blueprint the hull, rig properly and with that motor you could probably touch 53-54 mph, as long as you don't have a top.)

If you're not getting low 40-s for speed, you need to adjust the motor setup and most likely the propeller choice. You're not properly rigged and set up.