Need some jetting help
 

I think I need to rejet to lean out a bit and could use some advice. here are the motor specs:

350 CID
LT4 Hot Cam (hydraulic roller)
1.6 roller rockers
10:1 CR
performer RPM intake
650 demon (mech secondary)
vortec heads
TBIV ignition
34* total timing
k&n flame arrestor (9 in diameter, 2 in tall)
stock merc exhaust (thru transom)

it gets to 5000 pretty quick but wont rev any harder

boat is a 20 ft concord magnum II (weight is 2500-2800 lbs)

i feel like i should be able to get a 21 pitch to spin to 5400 but it just wont do it and im thinking its because its running fat

stock jets in the carb are 72 primary 80 secondary

please let me know what you guys think, just wanna get this thing dialed in a little better before the cold weather starts to set in.

Its probably not turning harder because of the stock exhaust.
You always start at the exhaust with any performance build.

that was my other thought, but im not sure what exhaust to go with, lots of flavors to choose from out there and i cant swing the high end headers. any recomendations on what exhaust would work good with this setup? keep in mind im running a silent choice setup