Guys. I have a freshly built 383 with about 9.7 CR....Running a small cap GM distributor with the D1965 module...It's a quality one and actually advances the timing...What is a same total timing for this engine? I used ten degrees initial and it seemed like too much....thank you...

what heads, what lowest octane youll ever run ?

93 and vortec..Thx

I would run between 32 and 34 total timing.

Why do you say that ?

Personally I think you are skating on thin ice with that compression ratio and iron heads. Vortec heads typically do not need as much timing as "traditional" Small Block heads so 32 might be a good starting point. You need somebody who is good at reading plugs but it needs to be done after a long hard pull and shut off clean.

What fuel system ?

I ran a 355 with RHS Iron Vortec heads @ 10:1. It had a quench of 0.039". Total timing in was 30°. Ran great, no detonation issues, but I used a small factory marine FT cam. 202° Int..something like that, with 1.6 rockers.

87 oct non-ethanol.

I would not try that with regular SBC iron heads.

As Bill mentioned...you have to be dialed in, or there will be issues.

On a 383 with ~9.7:1, most setups like about 34-36° total timing around 3000 rpm. Set initial for good idle but focus on getting the total timing right with a timing light.

Have you tuned a sbc with vortec heads in a boat with 36 degrees iat 3000 before?

Not in a boat. 36 will knock 100%, 36 is perfect in a 69 camaro. The only way to know is check the ground strap heat line on a new spark plug. set the timing at 32 degrees total and go make a run with a new plug.

I think a few peeps are missing that OP stated Vortec heads.
I am in the 30-32* total timing camp also, you can try a little more but you need to know what you are looking for at that point.