Looking to try and make 500+hp. Have some Edelbrock performer rpm heads to go on it nice air gap intake and a Holley track warrior 850 carb
. Anyone got a good engine recipe to be able to run 87 non ethanol. (Can buy on water)

current engine is 468cu. With flat top pistons. Should be in the 9.2:1 -9.5:1 compression range I think.

Gonna go through engine before putting in boat. 25 warlock cat.

I could be wrong but you might need 93 to reach your goal.

Agreed.

GM’s ZZ502 crate engine uses those same heads with a similar CR to make 500+ hp. That cam sucks for marine use but the Crane 731 is slightly bigger and more marine friendly. That should get you where you need to be.

The 731 cam with 9.5 SCR would give a DCR of 7.1:1 even at 4 deg advanced. With aluminum heads, smoothing out any sharp edges on the chambers, running it at 160, and making sure your head gasket gives a good quench, I think you could get away with 87, especially if you don't have static timing.
I currently have a 9.1:1 454 with 6.9 DCR and running 87 no problem with timing at 36 deg all in.

First question and probably the most important - what exhaust do you plan on running?

I’m running about 10.5CR with a 525EFI cam that helps bleed off some pressure. I blended the chambers on my heads to smooth out any hot spots as the castings have a good deal of frag on them. I always run 93 just to be safe at 32° timing and 12.5AFR. The blending removed about 10cc of material and went with a 0.027 MLS head gasket to keep the quench in spec

No way are you anywhere near 9.5:1 with flat top pistons in a 468 with those heads

That is a good point...didn't think of that.

Who dis?

I had to add 17cc domes to get mine up to 10.5:1

What fuel and cam did you run with that?