M90A idle?

I'm trying to tune the carbs on my 90 (non TLDI obviously) as per the factory service manual and wondering if there is any advice.

I did the link, sync and timing as per the manual, now onto setting the idle and the mixture screws. The issue I have is that I can't get the engine to idle at 1100 rpm in neutral/900 in gear. If I tune it for 900 in gear, it idles at nearly 1500 in neutral. If I tune it for 1100 in neutral, it will drop down to 6-700 in gear. This is being done in the water, not tied to a dock etc (boat moving). How do you guys usually set these up? Any issues with running the idle down to 6-700 in gear? It seems to run fine at those speeds (doesn't stall).

Thanks...

I first verify the throttle is synced. Then start with mixture screws about 2 turns out. Then adjust the idle stop where I want it. Then go back and readjust the mixtures for highest idle. Then readjust the idle stop. And repeat a few times. Yes, that 700 is a bit slow, and it will likely foul plugs, plus maybe not get a good hole shot.