Is anyone using an aftermarket ecm on a modified 500efi engine.
Just wondering what's out there already. To scrap the mefi

I run the Holley HP EFI on mine. Works great!

Holley HP EFI

That's what I have been looking at and the fast efi 2.0.
How hard was it to replace the harnesses and make the connections to the dash harness

MS3 Pro will be running that for 2017

Bi. What do u mean running that

I don't have 500 efi but I put a Gm LS in a boat using holley hp EFI. All in all I have about 10hrs of tuning which most of that was spent on idle quality and knock sensor tuning. It's crazy how easy it is.I have full control over everything timing,fuel,knock retard, boost control.

Holley HP on a 502 Mag. I had to splice 3 wires and all the sensors plugged right in. Real easy, I bet the 500 efi is about the same. I bought mine from Alex Haxby. He was very helpful and knowledgeable on the Holley

How did you tune the Knock Sensor?

Part throttle, steady cruise start adding timing till you can hear knock/watch the knock channel. Set that as a base line and tell it when it see's that to pull timing. I run with about 6-8 degree less timing then when it started to knock.

It also helps a ton of people have used the gen III LS motor so knock data is out there!!

Keep in mind that knock data different grossly in a boat then a car, motor mounting along with type of material it mounted to can change the level of knock