Boat seems to be missing 10 mph and 700 rpm

[Striper80]

I have a 99 wellcraft 22WA with a 98 Johnson 200 2 stroke on it. The boat is running the factory prop that I had redone. The factory claims this combo is good for 50 mph at 5800rpm, which I figure is quite generous. Right now at WOT I get 5100rpm at 28.3 knots. I'm not sure where to find those extra rpms. The prop is a raker 14 1/2 x 18 I've owned the boat for about 4 years now and it's been this way since. Compression is dead even 100 across the board, which I thought was low, but I'm told is good. My 130 Johnson had 150 on each cylinder with the same gauge. Did the carbs last year and link and sync, same. Throttle seems to be opening all the way as well. Ohmed out all the coils and checked timing on land. The bottom has bottom paint and it's king of rough, no growth though. The lower unit is an sei and it's supposed to be the right one for my application.