Has anyone ever used a MEFI 3 programed for a suppercharger on a stock 502 MPI engine.

No offense but that is a really bad idea. It would probably not casue any damage to the engine but it would run like a$$. If you are just using it as part of a diagnosis process that would be fine but if you are intending to leave installed on the boat it aint gonna work out so well.

It will need to be reprogrammed for you to use it. My guess is that about the only thing it will do is start and idle. It probably won't rev over 200 rpm because it will be overfueling at that point.

Is your engine supercharged? or is this a ECU you found that has been modified to run on a supersharged motor and yours is NA...
I run one programmed BY Precision marine but I do have a blower on my motor. It runs great!

do or notMy engine is not but the ECU that I got was set for a suppercharger.

Then you need to have it reprogrammed.

Sure let us know how it works out!!

All kidding aside, I think the guys have cleared that up for you.

Who do you suggest for reprogramming.

I've never had one done myself. Many people have recommend Mark at Precision Marine in the past.