What is the best exhaust manifold gasket for a 502? I have a set of Remflex, but have mixed emotions about using them. I know they are supposed to be good, but I have read a bunch of negative reviews lately.

Any graphite based wire reinforced will do. Mr Gasket makes the ones I use. You can reuse them.

Mr. Gasket copper are the only ones we will use. Re-usable and don’t have graphite that require hours of scraping to get all the crap off.

Kinda like the copper ones, but I guess I will go ahead and try out these Remflex gaskets, unless I find a reason not to. If I don't like them, I can always change to a different brand.

+1

I don't know what graphite gaskets YOU are using but the Mr Gasket ones have NEVER stuck to either surface and I have used them for many years.
I never had to scrape anything.

to each there own. I’ve had to scrape graphite off numerous heads when removing exhaust. Guess I don’t know what I’m talking about.

Had Remflex's for a '04 Ford Mustang Cobra. Returned them as the ports were smaller than the OE in the head.

Just adding some info for whomever. We have seen many issues with brand new Mercruiser engines with stock oem dry joint exhaust and especially if they had riser extension blocks having blown exhaust manifold gaskets, This was very common in 2004 thru 2009.

When I sold new boats it seemed in short order all ended up with blown manifold gaskets withing 5 hours to 50 hours was common. Some of the reasons were wrong manifold bolt torque from the OEM when new. Next was how heavy all that was / cast iron / exhaust manifold / extension block / riser. Also IMO the OEM gasket was not as good what others had to offer in the marketplace.

short jist was - we used Mr. Gasket Ultra seal exhaust manifold gaskets. But first of all --- checked all mounting flanges (manifolds ) and the engine side for flatness . 3 pass installation for the manifold bolts to the correct spec torque using quality torque wrenches. That was basically the cure for what we were seeing with blown OEM exhaust manifold gaskets.