82 fish nautique not reach top rpms

i have a 1982 fish nautique with a 351 ford crate motor. should be around 280-300hp. I am trying to figure out what size carb/fuel pump set up to use on the boat. im mostly used to cars so im not sure what it takes for this motor to get it up to full rpms.     

so far it has all new fuel system ex. fuel filer, fuel pick up, new hoses, new stock pump, new carb edelbrock 600cfm.   has msd ignition also.   the boat seems to have tons of power down low rpm, but i cant get it over 3800ish rpm at wot in gear, about 30knots. i feel this is not right. in neutral i can rev it well past 6000 rpm no problem. what i have been thinking is that it is starving for fuel. like the carb is not big enough or the fuel pump does not have enough output when the motor is under heavy load. although is could be ignition also although i feel like it is. im mostly curious to see what set up you guys are running on similar size motors and what rpms they are running at wot.

I have a 1:1 velvet drive.

keep in mind that the BBC's use a 600 cfm Holley. so i reaally dont think its a size issue, get on top of her while running, be careful, with a squirt bottle of gas...if she takes off its a fuel issue, if it boggs then its an ignition issue, thats down the throat of the carb BTW, after checking that the secondaries are opening up.
dont attempt this if you dont know what you are doing. disclaimer

Is the advance working in the distributor?