I am putting a 500 efi set up on my carbed engine. I have a MEFI 3 computer but I think that I have the wrong efi harness. The harness that i have has the electronic spark module in it. I bought the unit used and don't know if was a running unit??? Does anybody out there have a mefi 3 computer controled engine that uses the spark module?? Or is this harness for a mefi 1 only or can I use the harness and bypass the spark module. Please any help would be great. I bought the unit 2 years ago here off this site but I can't remeber from who to ask them any ?'s thanks for your time.

Will this help?

From Service Manual 6 - Mercruiser Hi-Performance GM 500 EFI Engine.

Thanks Hydro, I spent the whole day looking at that pic at my local marina. i also looked at Bam Marine. my concern is the spark module I know that in that pic there is no module but in another diagram at bam they show a mefi3 set up that does have the module. So I'm cofused does or does'nt a mefi 3 use a spark module?

This one? #9

I dont think the 500 EFI ever used the MEFI 1 but I am not sure.

Yes mine is the middle one but my harness has the spark module. does mefi3 use the spark mod. or does it controle spark through the computer?

I belive it's controlled by the MEFI3. This is the wiring for a 502 Magnum does your's look anything like this?

Yes it looks just like that one is that the one that I should be using or do I need the one for a 500 efi that is listed in the high perf section at bam marine?

The only differrece that i can see between the one that I have and the 500 efi one is the spark mod. If you go to Bam and go to the high perf. sec. then to the 500efi look-up then efi wiring you will see what I meen.

If you are talking about the KS module, it is not used with a MEFI-3.

Hey Freekie

Stop by my house. I have both of my motors apart in my garage for the next week or so.

Smitty