i don,t know what your budget is but if you want 650 hp and and an engine that will last i would build a 540.good quality rotating assembly with the eq heads can make 650 all day long.if you are starting out with no intake or carb i would go with a single plane intake for a 4500 series carb and a holley gen 3 dominator 1050 carb.for a camshaft i like the crane 651 hyd roller and it is a perfect match for what you are looking to do.i like the comp cams short travel lifters and have had good luck with several sets i have used in marine applications.i have not used johnson lifters so i can,t say if they are good or bad but i see guys claiming good results with them.i would stay away from the morel,s as their quality seems to have slipped away.some guys feel the need to reinvent the wheel but i see no need for that.their are plenty of 540 marine engines built with off the shelf parts doing the job.also,your new exhaust with dry tails will work great for 650 hp.

I have a set of GM 6.135" forged Performance Parts rods and JE forged pistons for a 4.560 bore that I will let go cheap if your interested. I have a 524 that I built with AFR 305's with CNC chambers and bowls to save money and blended the runners with the single plane intake myself. I'm running 10.1:1 compression with Diamond pistons. I built this a while back when Morel was still making good stuff and a custom cam with .623/.611 lift and 242/252 @ .050 with a 112 separation angle. I have the Crower Pro Magnum rockers, Ferrea valves and Isky springs with a stud girdle. I run a modified 950 carb and lightning headers. I never dyno'd it, but I've run 90 with 4 people on board in a Velocity 280 so I know I'm over the 650 mark. I bought the boat with 50 hours on it and it had been sitting so long the bores had rusted and I needed to hone it out to clean them up they were so bad.

mine made 652 hp and i didnt even use cnc ported heads. 557 cubes, 1050 quick fuel, 9.3 to 1 compression. idles like stock, what your doing like others said is easy.

540CI
9.5:1
AFR325 bowl and chamber CNC
cam was 241/[email protected] and .680/.663 lift on 112
1.7 rockers
Single plane intake 4150
1050 QF carb 4150

these engines made 630 hp on dyno in full marine trim, so probably around 660 or so dyno trim, I would swap that cam for a shelf grind that is easier on the valvetrain, but that was a recipe with a dyno result I had.

UPDATE

Thinking about a SCAT rotating assembly, Forged crank, H beam rods, Wiseco pistons is 10.5 compression ok on 90 octane, ethanol free fuel

I wouldnt run 10:5:1 on 90 octane. Ethanol free doesnt mean you can run more compression.

For 90 octane, id keep it in the 9.5:1 range myself. Jmo

I can run Ethanol at 93 if I set it up that way, is 10.5 with 93 octane OK

I agree with all that ^^^^ 9.5 :1 performance marine build 90 to 91 octane. We have been using 91 pump gas and yes my area is all E 10.

ok ordered cams 651 cranes,

what lifters should i buy