Looks like they opted for a plate system to go from TRS to Bravo transom pattern. Though I'm not sure you would need to make such a large hole to achieve the aim.

Yes, precisely. We opted for a conversion plate system to switch from the old TRS footprint to the Bravo setup.

I am fully aware that the 'plates vs. filling the transom' topic is a subject of endless debate in the community. However, we made a very conscious decision to go down this route.
When we stripped the rigging, we found the original transom core to be in exceptionally good condition—it was bone dry and rock solid. We decided it was better to preserve that original factory structural integrity rather than performing invasive 'transom surgery' when it wasn't technically necessary.

The system has been absolutely rock solid and trouble-free for us so far, so we are happy with the decision.

Guys, you are steering me in a very exciting direction here. Thanks again for diggin in!

The Brodix 'Race-Rite' Revelation:
I looked up the specs for the Brodix Race-Rite BB-3 XTRA O based on your recommendations, and I found something very interesting in their 'Easy Order' chart (see attached screenshot).
They actually list specific part numbers (e.g., 2068123) that come with 115cc chambers right out of the box.

My Conclusion / The New Plan:
If Brodix offers them at 115cc, that tells me there is plenty of 'meat' on the deck to mill them safely.
Since the Edelbrocks are unobtainium anyway, my plan is now shifting to this Brodix Custom Approach:

1. Buy Bare Casting: Order the #2068001 (Bare, 119cc chamber, Stock Exhaust Location).
2. Local Milling: Have my engine builder here in Germany flat mill them down to 110cc.
   • The Math: According to the Brodix spec sheet (Flat Milling .0050 in Per cc), I need to remove 9cc.
   • The Cut: 9 x .0050 = .045" cut.

My Sanity Check Questions to you guys:

1. Safety of the Cut: Is a .045" flat mill considered 'safe' on these Brodix castings for a marine endurance application? Or does the deck get too thin?
2. Intake Fitment: With a .045" cut, I know I'll have to machine the intake manifold faces or the head intake surface. Is this still manageable with standard intake gaskets, or am I creating a geometry nightmare?
3. Real World Experience: Has anyone here run a similar "Heavy Boat / 502 / Milled Brodix" setup? I can't imagine I'm the first one trying to build a high-torque 502 for a Café Racer / Gun Boat without using a blower.

If I get the green light on the milling, I think this Brodix setup (better flow + high compression + stock exhaust location) will actually end up being superior to my original Edelbrock plan.

Cheers,
Stefan

Thanks for digging up the specific AFR stats!
Those 290cc heads with the 112cc chamber option are definitely a 'tasty' choice technically. Under different circumstances, that would be my go-to to save on the machine work.

However, looking closer at my exhaust setup (see attached pics), I think the AFRs might cause me a headache during installation:
I am running stainless CMI-style headers with fairly rigid plumbing through the transom. I don't have long soft rubber couplers that could easily absorb the ~.375" raised exhaust port height of the AFRs.
I am worried that the higher port location would put the whole system under tension or cause alignment issues at the transom rings.

That’s why I am leaning so heavily towards the Brodix Race-Rite: The guaranteed 'Stock Exhaust Location' is a huge safety factor for my rigging. I'd rather spend the extra effort on milling the Brodix heads than fighting with exhaust alignment later on.

I guess, I’ll stick to the Brodix plan for now to keep it a clean bolt-on process.

Are Bravo XRs OK for 550hp with the level of torque you are intending?

Dont you want to remove 5 x .005” to remove 5CCs?

I don’t know about these specifically but I know some aftermarket heads typically have a 0.500” deck thickness.

as they're being used without any problems with the mercury racing 565 engines, I guess, I'll be safe with my intended setup.

Important to note that the 3/8" raised exhaust ports...move the exhaust manifolds out 3/8" at a 45° angle. Your outwards and upwards movement would be 0.265" each.

So exhaust manifolds between engines... would lose 0.265" × 2. 0.530".

AFRs typically have 3/4" decks.

109cc on the AFR 265

https://www.airflowresearch.com/265c...nder-head/p603



That is a tiny head and valve that gives up a lot of flow up top though.