The stock Gm single wire is the one most use. I used stock 502mag on my last build and same part number on my current build.

What knock sensor frequency do you use in the Holley set up?

If you refer to the system I was referring to, to the other member, you can not run boost.
The Sniper EFI system will not do it.

And your Youtube vid didn't work! I need to see some engines running:)

Anybody out there running the Holley HP EFI on a Mercruiser 496HO based engine?

I may have missed this in an earlier comment
But what about converting or connecting the ecm and engine harness to the existing boat harness. How hard is it to make the big plug conversion

Also does anyone have any experience with using the fast efi 2.0
setup on our mpi ramjet intakes

Fairly straight forward, depending on what you are starting with. I just say that because the 502 charging harness and the 500EFI charging harness are different. But on mine, the 500.. There is a Key on, tach, blue with tan and tan with blue for alarms and temp. The 500 has water temp going thru the ECU, so its slightly different. Then you make the plug on the other end to match the Holley pigtails.

I made the switch a couple years ago from Bravo drives to Arnesons (with BAM transmissions) and I turn 34p 18" diameter SSM #6 props. Shifting in gear usually causes a stall (drops RPM from 1000 to 500) - IF I don't touch the throttle. I've learned to bump the throttle slightly (more air) and it reacts normally without a change in RPM. It seems the IAC doesn't react quickly enough to overcome this. The issue here is you need to have lots of hands in a tough docking situation.

I run the HP EFI on my NA 540's with multiport injection and DIS ignition. My cams aren't too wild, but the engines currently don't like to idle much below 600 (with carbs 750 used to be iffy).

I'm curious what idle tuning you can do to help big-propped boats fine tune this and counteract the stall? I've tried several techniques, curious what the pro's do?

This is what solved the stalling for me and I was taught about this by Alex Haxby . On the timing table note which cells you idle in. I set the timing to about 8 degrees in these cells. Now I look at the cells I move to when I bump the boat into gear. I advance the timing to 22 degrees in those cells. The timing will react much quicker than the IAC motor and help save the stall.

Tibb like Hadley stated its all in the timing. I've got 33's on my fountain and it took 20-30 min to get both motors acting right in and out of gear. I run more than 22deg in gear and that has helped me. If you need any help your more than welcome to call me. 317-538-3100. Haxby has saved me tons of time over the last two builds. He is the man!!