Can a ECM4 be made to work inplace of a ECM3

Yes, you just have to re-arrange the pins on the wiring harness since the MEFI4 pinout is different. Also have to get the 4 set up with the same configuration.

I have switched from a 3 to 4 a month ago and its working fine.

Advantage 27

Where can i get the pin configuration information.

Were you ever able to get the information to do this?

I have the pinout to go from a 3 to a 4 if you still need it. Give me a shout and I can send it to you.
Eddie

Not trying to hyjack, question along similar lines, can a 555 on a 496 be replaced with a properly programed MEFI4 ?

Is there a harness/plug adaptor that plugs into the 496 harness and changes the 555 plug to a MEFI 4 or am I talking out my as$.....?

Interesting? Any body?

The only way to replace a 555 with a mefi is to change the harness. There aren't any adapters to convert it. The wiring harnesses are totally different.
Eddie

Thanks for that Eddie, do you know what MEFI harness would work on a 496 that is currently 555? Procharged application so would like to be able to program the ECM......

Hey Jer, the harnesses are available from a couple different manufacturers, Volvo, Marine Power, Kodiak. Merc was the only one not using a MEFI on the 496. I've got the HO base program I can send you if you need it and may have a harness too. I'll check and let you know.