i have twin gen 6 502 efi motors. I've had nothing but problems with them. Port motor has 50 hours and starboard has 1 hour on it, both completely stock engines. Looking for recommendation on carbs to get. Eliminating the fuel injection

Quickfuel 850m and Victor Jr. manifolds should do the trick.

Agreed. Unless you are a 3500 to 4500 rpm kind of guy. Then you want dual plane intakes. The stock Mercruiser one with the bronze water passage across the front is a very good intake. Now, your ignition system. You have delco EST. You need delco voyager modules or you will have no advance. Or get 2 large cap HEI distributors and get the blank-off plates to eliminate the vac advance cans.

I've never seen a 502 mag mpi engines that cant be fixed, what are they doing wrong and who's been working on them, changing to carb doesn't guarantee trouble free boating

The DUI distributor has worked well for me. Just plug in the tach lead and one 12g power wire and you're up and running.

The DUI is a 400 dollar large cap HEI.

The existing distributors will work fine.

I have a band new HEI distributor for a $100.00

He can use his current EFI distributor, without computer control of course. The module inside should have a short advance curve built in, if not, the appropiate GM module is about $70.00 . If you want to go with a killer ignition with programmable advance curves, rev limit, idle stabilization, and etc, you can use the same distributor, but bypass the module and add the Daytona Sensors Marine Ignition Box and coil.

He can use his current EFI distributor, without computer control of course. The module inside should have a short and real quick advance curve built in, if not the appropiate GM module D1965A is about $70.00 . Advance is 22* and super quick. If you want to go with a killer ignition with programmable advance curves, rev limit, idle stabilization, and etc, you can use the same distributor, but bypass the module and add the Daytona Sensors Marine Ignition Box and coil.