The ones that have advance built in should have the advance shown in graph on right side of this page:

SB Thanks, yes that is exactly my distributor. I will see what GM part number I have and proceed. Hopefully my Chevrolet parts guru can get the info. I need.

For reference, the carbed HP500 uses the V8-HP module.

For those wondering, he PM'd me and he is thinking about swapping the EFI system on very low hour 500EFI over to carb system.
My opinion was..........
I would 100% leave it as is with the stock EFI. Buy a Rinda Scanner and Merc Racing factory service manual.
Swapping to a carb will devalue the boat overall by several thousand $$ and your fuel economy will drop by 10%.

I can't for the life of me figure out why people would want to replace a working EFI system with a carb. I want to swap the carbs on my cat for EFI.

One thing that most people don't think about is the floats and fuel levels in a carb while you are hammering in the rough. I don't think EFI even know what's going on with water conditions. Just the air that's come by in. That's my biggest reason for EFI

Thanks for everyone's replies and opinions. They are all valid pros and cons. My frustration in the past has been not being able to accurately diagnose some running issues. At this point I am not 100% sold on switching to a carb. My boat before this one was carbed and as I remember there were no issues running in the rough stuff at LOTO. Just have to see how it all plays out.

FWIW,

If you are willing to tow to Wichita I can fix it for you.

Thanks