Hopefully someone can solve this mystery for me. I am truly about to have my head explode with frustration trying to sift through the bull ****. I am only asking for help here since I have done tons of research myself, and spinning my wheels.

My goal is to purchase a new 502 (reman or spec built not option).

Where is the best priced place to purchase a Marine Duty 502, with iron heads. Just looking for the bone stock 415HP version for a MEF1 I purchased to install.

Is there any difference in the short block for the Merc 502 Vs. GM 502 Vs. GM Marine 502, other than oil pan and needing to change oil valves? Bearing and ring clearances the same? Reason I ask this, is it seems one option is to purchase a GM 502 Short Block and put on some built iron heads. But then stuff gets confusing again on this. Probably have to change out the cam to what is needed for the MEF1? And in doing that, would it be installed with any degree, or straight up? I do not even know where to find an answer on this.

Feeling a little over my head on all this. Long block is looking best, but why donate over $1000 to Merc's marketing department if it is not needed. Merc 502 Vs. GM 502 Vs. GM Marine 502. Any good info would be helpful.

BTW - I am in California.

-Rich

I'm sure someone will provide you with useful specifics. My answer is going to be that if you buy the Merc you don't have any more questions to ask.

if you buy a merc reman you get the same warranty for a lot less than new,just saying.

I'm surprised nobody mentioned marine cam.

Im guessing you dont have a core or the kind of core that can make the reman program appealing.
Or maybe you have one thats a little too good .
There is nothing wrong with a good gen 4 stroker 496 either , i have a buddy that bought one with dart heads for 3500, sold his 454 mag core for 1000

Why isn't a reman an option? It sounds like you want to be once and done with this, so I'd go with the Merc unit if I were you. That extra $1k buys more than just marketing hype.

The core I have is a 454, so as air junky noted, reman is almost same as new. I was going to use some of my 454 accys, but at this point, I will mostly purchase new or like new accys. Already have a MAG 502 MEFI 1 set up to bolt onto a 502 long block.

Found what I believe is a good deal on GM Marine (6600 plus shipping). Just a shadow of doubt, as it is GM Marine, not Merc. But - For a 502 long block, I can't identify any difference from the GM marine from a Mercruiser long block. I think I ready to do it and move on, but sure wish I could identify if there was any discernable difference.

GM made all the Merc blocks, 454 502...........if it has 8.2 in the casting on the side of the block, its GM 502

I do not believe, that Mercury/Mercruiser, assembles their black sterndrive engines in house, by machinery, or by hand. From what I recall, they purchase long blocks from General Motors , and rig/dress them in house. As did companies like Crusader, Volvo Penta, etc.

The 502 crate engine, you could get from chevy dealer, or summit, etc, has the same rods, pistons, block, timing chain, heads, valves, rockers, and so on, that a 502 magnum has. I highly doubt, that the "marine" versions, got special piston to wall clearances, ring gaps, guide clearance, etc. The camshafts were different, but still a GM camshaft, and GM lifters in the 502 and 454 mags .

The blue mercury racing engines, are a different story.

If you truly want a zero headache project, you will be money and frustration ahead to steer clear of the MEFI 1 setup.
I assume it is used, and they have been out of production for a long time. So you know the wiring is old, the injectors are old, and
who knows if the ECU still has the original programing, without purchasing the needed software to check it out.

I went through all of that a few years back, finally got smart and purchased the Holley HP TBI, Best money I ever spent. If that's out of your budget, then
I would go with a carb, and go boating.

Steve H