Now back on track thanks for the input

You dont time an engine based on a particular number. Combustion chamber design, camshaft, quench, spark plug type, fuel mixture, octane level, air density, air temperature, piston speed, all play a factor in what determines the "right " amount of timing.

Excessively retarded ignition timing, can superheat the exhaust temperatures, and quickly take its toll on exhaust valves , and exhaust valve seats.

I personally would run from an engine builder that thinks 32 degrees of timing is the key to a marine engine warranty. Let me guess, he likes "locked" timing too

I had great experience with my guy solid reliable 600 hp out of my 509 I made the call to use iron heads and that was a mistake I like to see what others are using and see there experiences

A few of us are running iron heads on supercharged engines making 800, 900 plus horsepower on pump gas. Why was iron a "mistake" on your 600hp NA engine?

My iron heads seem to work just fine with my 600hp NAs

Since it sounds like you are sold on aluminum heads solving your issues, whatever they may be,

What kind of power are you looking to make ? Single engine or twin engine boat? What max rpm would you be looking to turn? Is this going to be a hydraulic roller, solid roller, flat tappet, etc?

What exhaust are you running ? How hard do you run your boat ? Are you in freshwater ? Do you keep your boat in the water or on a trailer/lift?

Is idle quality a priority ? An engine with the same camshaft but different intake valve diameters can have an effect on low speed intake reversion, as well as low speed torque

Are you buying them complete and plan to bolt on, or looking for a bare casting to have your machinist go thru and set up?

There stock iron heads Merlin and I can feel the motor is starving for more should have had the heads flowed that was The mistake

at 600 at the crank now would like to be at 650 to 680 crank
Harden exhaust manifolds dry risers
single motor
boat is keep on a lift
salt water
hydraulic roller lifter
heads up would be bare cast and build up
Not sold on aluminum
850 quick fueL
afr at crus 4k 13.9 50 mph
afr at wot 12.1 70 mph 5200
prop 5 blade 24 hydro px5
- 2 short speed master 1.5 ratio
prop slip 12
max rpm 5600 would like to see

My iron heads 900 hp, no intercooler, 36* of timing and 900 hp doesn`t seem to be a 'mistake' . Runs like a champ.
Thinking aluminum is somehow going to be some magic saviour .. it`s not ... It`s lighter and you need more timing thats about it . Plus in salt water that can`t be very good for longevity.

I sure as hell don`t run 13.9AFR at peak tq thou. I`d have some large holes in pistons for sure .

Sure I could slap a blower on and make 800 hp but that's not what I want to due looking for input on what people are using the pro and cons sure I could slap a set of dart heads on looking to see if anyone is runnning a 509 with aluminum heads and see what type of power there getting in a single engine boat if I went the route of aluminum I would add a closed cooling system motor side

thanks for the input