I don't think you'll have any issues with getting it to idle fine after playing with the idle air bleed screws. I ran an HP500 carb(rejetted) on warmed over 454mag with a stock intake and 1" spacer. It idled fine around 850rpms in nuetral/700rpms in gear.

The best way to do it is to get the model # off the air horn and look up the factory jet sizes Holley sent for the carb. That is a good start point. If you cant find the jet sizes shoot Holley a email and they will respond in a few days. Guessing at sizes to start is a crap shot. Plug reading is difficult with ethanol fuel to get it right. Look for a good soot on the outer ring of the plug

That's how I came up with 77 and 91. Stock is 72 and 87 and I find adding 4-5 sizes for marine is generally very close to optimal. Keeping the split from the box stock even is a good idea.

stock HP500 jets
Primaries 81/75
Secondaries 89/93

I wonder why they did that,considering the
intake was open plenum you wouldnt think it would need
different sized jets?

Thanks Griff,
, I was hoping for a bit lower though, I had the 454 idling at
675 out/ 600 in ,, one of the ways I have kept drive alive.
Thats why I want to know what all my options are. I have been told the stock
502 efi cam should idle very low no problem so my only concern is carb wise (I hope)

I had quite a bit more cam in it than stock. Sold the boat to friend and the original bravo drive is still on the boat with about 700hrs.

Sounds good then..
Thanks