Having problem with my 502 mag dying after being run for 20-30 minutes. Dies and just will crank with a little spitting and sputtering. Let it sit and cool off for a few hours it fires right back up just fine. Any ideas?

Sounds like vapor lock. These motors are notorious for vapor lock especially with the VST system, but will also do it on the cool fuel 502's.

Do a search on here and you'll find a bunch of topics.

exactly

I have never had the engine die while running around, mine would just not start after an extended shutdown, maybe but it could be electrical as well.

Many of us have/had same problem on 502 MPI's. I went the Merc route and installed their add-on pump. It worked really well, and I never had the issue again (you can install this yourself easily). Others have run return lines back to tank, installed better pumps, etc. Many ways to skin a cat.

If you happen to venture out again and this happens check and see if you have spark, could be a coil about to take a crap.

Thanks for the info. This motor has the mechanical pump on the sea water pulley, is that the add on you are referring too? If so I replaced it this winter

Mechanical pump feeds the electric fuel pump inside the VST located above# 7 cylinder. Unless your carb 502 mag.