I spun a rear main bearing in my port 500 efi. I was wondering if Mercury used a stock high performance short block for their 500 efi short blocks? Or did they assemble their own short blocks? If they did not use the gm assembly what are the differences? The top end of my engine was completely redone about 100 hours ago and it looks great. I'm just trying to get back on the water as soon as possible, so I'm looking into as many options as I can.

Are the marine block different alloys or do they use the same block marine and auto?

Thanks in advance,
Jeff

Yes
Other than the camshaft, it's all the same stuff.

Is the ZZ502 the one I would want to get to replace the 500 efi?

Absolutely... Just use your stock 500EFI camshaft.

Most of the 500 EFI's used a manley H beam rod.

I dont think the ZZ502 does.

I think I remember somebody that was giving me a quote on a rebuild said they we would upgrade the rods h beam rods, so I'm not sure if they come with the h beam rods or not.

Absolutely not...

Mine did and they say Merc Racing on them.

As did the pair of 02's I just did.

Perhaps the H beam rod is something they started in the later 500EFI's. I've done quite a few 500's, the newest ones being a pair from an '02 Top Gun, and have never seen anything in them but a GM rod. Obviously, they must have used them in some of the later ones.