Bingo! not only pressure but volume how big is the fuel line, foot valve stuck, filters clean,some thing stuck in fuel line?. I know from experience I go into panic mode sometimes and forget the basics, check fuel system before tearing into engine
my .02

well... we've had this discussion before. the drag profile of this boat is very high at 70 mph. you need a LOT more hp to go only a little bit faster and there are a dozen threads here that deal with those ACCURATE mathematics. two things strike me here...

1) there is nothing in the work thats been done to suggest a giant increase in power

2) the original combination that seemed to work well, has been comprehensively changed to some OTHER combination of unknown capability.

you say it runs great down low but won't pull up top... yet thats what you told them to do. if someone said that to me , the cam would go in well advanced and the i would be after big port velocity as opposed to big flow numbers... yet it seems that you went after the flow numbers as well...

i wonder if the combination is just wrong and while you have punched up the middle it falls over and runs out of torque too soon up top.

spend the money. go to the dyno and find out the truth before you piss away the summer and a bunch of money guessing.

I am carrying at the carb 6psi at WOT. The anit siphon valve is that done in the tank. my fuel line from the top of the tank to pump 5/8 from pump to carb -6

Listen to what stevesxm is telling you.

If the cam specs where posted I apologize for asking since I only saw lift figures.

What are the seat, duration at .050", LSA, or better yet Manufacturer and cam part# ?

I know Comp makes some 'snotty' lobes with mid .500's lift so I wonder why we think the cam he has is close to 420 Specs ? As far as I read, we don't know.

Again, if I missed the specs, I apologize for the questions/statements.

Check the float level on the carb. And yes I agree on the dyno first , in the boat second the best money you will ever spend Good luck Jeff

Answer the exhaust and cam duration question.

Pt # 11-000-47; SN# N3994-08; @.050 230in; 236ex 112 lobe separatiion; duration @.006 tappet lift 274in; 286 ex

So I am guess set of rect. port heads and a larger cam

Not an expert, but could the Air-Gap dual plane intake manifold be a contributing factor? If you're claiming "a ton of more power/incredible low and midrange" as you say, then I am highly suspect that the "Air-Gap" dual plane intake manifold may be what is restricting and holding you back. I'M NOT SAYING IT IS THE ANSWER, but I certainly do not think a dual plane intake is helping you any in the upper RPM ranges---especially on a 496cid engine with properly selected/ported heads and exhaust headers!

Could it be some of the other problems that some of the other guys have suggested???---YES! I'm not discounting any of that, but if the engine is telling you all the power is from low to midrange then the torque range needs to move towards the RPM scale from midrange to top end side. Just a suggestion---something you might consider. Hope it goes well for you.