The 731 cam is not at all radical. Its just slightly bigger than a hp500 cam. It should idle fine.

Just got back from a vacuum test from the dock , at 800 rpm in gear the vacuum is 7.5 . I only have one PV in the front which is a 4.5 no PV in the back with the marine carb. AT 1000 rpm the vacuum is 13 inches.

Do you normally run at 800 RPM in gear? I can't do that with my set up or my RPM in neutral would be 1400 RPM. If I shift into gear at 1400 RPM I am likely to stick the clutches....did it once. I have to run close to 650 RPM in gear to lower the RPM in neutral to 1200-1250 RPM...still a little high but hasn't been an issue.
Bottom line is that the PV opening at idle is not an issue with your combination.
Sorry my suggestions didn't help your stalling at idle.

A 600 rpm drop into gear???????? Way too much. Something is not right.

Bravo's do not like any shifting with more than 1000rpms

Thats right Ben. You probably need to crack open the secondary throttle plates a bit and back down on the primary idle screw to keep the primaries on the idle circuit.

You could do what I said earlier alec but add to that change out that 4.5pv for a 6.5pv.

how far are the air screws turned???if 1 full turn i would go more and see if it will go into gear and not stall....

Blue,
Thanks for the comments. I currently have the primary throttle blades set with .020-.025" of the transfer slots exposed. I set the RPM with the secondary TB's only. We also have additional adjustable air bleeds drilled and tapped into to top of the carb body for air adjustability at idle (better system than drilling holes in the throttle blades).
On my last trip, we had the idle in and out of gear in pretty good shape with no stalling. Currently I am focused on the A/F ratio with a mid-range target of 13.5 to 1 and WOT at 12.5 to 1. We want to accomplish this without a lean spot before the PV's open. With any luck, we will be dialed in by the end of the day on Saturday.
My 2007 idle issues were caused when I went from no PV's to 3.5's. My PV sizing error was caused by measuring the vacuum out of gear (6-7") vs in gear at 2.0-2.5"....big cam. I report how it all works out next week.
As soon as I get this figured out, it will be time to switch to EFI so not don't run out of projects!

Sounds like you have it well under control Ben. Tomorrow should be o2 A/F day for me too. Hopefully I can get these 1050s w/ blowers to run like my 800s.

Still working on the idle. The 2.5 PV didn't work as the AF ratio had climbed at 14.1 @ 6000 RPM w/o the PV opening!..I backed off. With the current jetting and a 3.5 PV's, the AF ratio from 3000-5200RPM is steady @ 13.5-13.6. At 5300 RPM, the 3.5 PV opens and the AF ratio drops to 12.5-12.6. I am good with this...but I am still working on the idle spread in and out of gear. The 3.5 PV will remain closed at 700-750 RPM in gear, but the high RPM in neutral remains the issue. (trying to not jack with the throttle in and out of gear)
Looking at some other comments on this thread, it as occurred to me the MSD ignition with the mechanical advance may be an issue. I never had these idle variances with the Merc Thunderbolt IV and the V-6 box. My total timing is 40 degrees.
Looking at the MSD website and the various distributor spring combinations, it appears the MSD timing curve advances 3-4 degrees from 700-1200RPM. This seems to indicate that locking out the timing advance could be a good method to reduce the RPM spread going from in-gear to neutral. On my next trip, I will see what the timing difference is between 700 & 1200 RPM.
Is this thinking on track? Comments?

If you don't have a vacuum leak and engine is healthy (compression is good) it sounds like you are having a timing issue somewhere.

With anywhere from 12-18 degrees initial timing that motor should idle very smoothly.

I don't like weights/springs/bushings in marine distributors. Too many compromises. Electronic advance curves can be much better.