The current one’s aren’t GM, those prior to 2015 were GM based
as already mentioned above

If the 350 is not a GM then what is it?
Take a virgin bore 350 with stroker crank and you get 377

The 502 is still the GM casting its just being made by Merc

merc makes their own 502 cast iron blocks?

i know how they got to 377ci just wasn’t sure which sbc Gen engine family it’s from

Dont think so

A 350 with a 400 crank makes a 383
A 400 with a 350 crank makes a 377

a 350 with a stock bore is a 377. It’s a 383@ .030 over and 388 @ .060 over.

The MerCruiser 6.2L was a GM 5.7L engine that they disassembled and built into a 6.2L.
Then a few years ago they started casting their own aluminum block 6.2L. We are told this new engine uses NO GM sourced components.

Quick way to tell which engine you’re looking at is to look at the throttle body. If it faces away from the pullys, it is a Mercury Marine block.

Interesting. I see it is 4”x3.75”. Any idea if it is just a copy of a GM small block?

I don’t know.

FWIW, if the OP was asking about the pre 2015 320HP 6.2L. Those were simply the 4" bore, 3.75" stroke "Vortec" based GM engines.

According to this article: All New 6.2 It claims the "new" 6.2 is a clean sheet in house design. States it has 65% common parts with the in house designed 4.5L 6 cyl.

Also states twice in the article the block is IRON.