just looking on where i should run my timming on my boat. sbc with stainless marine headers, 72 cc rhs heads, cam, 750 holley, 8.5 to 1 compression. 93 oct gas alway run in it. msd ignition

Rhs heads have a decent combustion chamber, what pistons? If your sure it's 8.5:1 93 is way over kill 89 is plenty safe and will make more power. (very little but more) 34* worked well when I had those heads on a 406. Cam duration timing and lsa will play a factor also.

I'll only throw this out for reference:

95 Merc 350 Mag EFI/MP motor ran 36-38 degrees at 3200 rpm or so and it tapered off at higher MAP settings. This was with stock heads and stock 9.35:1 compression on 87 octane.

I would agree that 93 octane with 8.5 C/R is fairly conservative.

Start about 30, walk it out 2 degrees at a time doing a wide open throttle run each time. when it stops picking up speed or pings, set it back 2 degrees and that's where it should be, Sometimes I'm surprised at how munch timing a particular engine likes or doesn't like... OH, and do this with the lowest octane fuel you will be using...

I also agree with above, you've got no reason to run premium gas in that engine.

+1 but also stop at 36 unless you wan't trouble...