I will have to ask the dyno guy. Is that something he would have set up? I am not much on this motor stuff. I can't really answer many answers on my own. I don't knw much about this stuff.

Right now it has the 850 but I can switch it over. I wanted to see if the 850 had the same results as the 1050. Which it did.

Keep the dominator at minimum. You picked up 38HP over the 850. (I would not be surprised if you picked up another 38HP with twin 750's on your setup)

When I had the 250 and single dominator, I had to back my idle mixture screws out 2 or 2.5 turns to keep it from stalling when shifting. It was basically borderline needing different air bleeds for the idle, but it worked.

I seem to be battleing the same issue. I think the mixture over leans when the rpm drops when shifted. Wireing the choke partly closed seems to make it shift okay. I may wire a small solonoid to the choke triggered by the shift mechanism I was told Stirling did something like this in the past with Blower motors.

I believe what sterling did was use a throttle advance solenoid, wired to a shift switch. When shifted into gear, the little solenoid would open the throttle blades a touch, helping to keep engine running. They didn't use chokes on their carbs as far as I know.

If the 850 has 4 corner idle make sure the front & rear throttle plates are open the same amount. If you get the throttle plates too far open it will expose too much of the transfer slots. you should have about .040 of the transfer slots showing.

He probably set the max advance which you stated as 34deg. The timing curve in the distributor determines how far it will advance from idle. I don't know how DUI sets up their timing curve in the distributor, but you are dealing with a HP non stock engine, so some tweeking to get things right are not uncommon. I would see if you can get your guy to go with you and change the base timing at the dock to see if advancing it more will allow it to shift into gear smoothly. Then you will know if your problem is the timing or the carburator. If it works with advancing the timing then you need to take the distributor to a performance speed shop to have the timing curve changed so it idles at that majical advance number and only advance to 34-36deg (wherever your engine builder wants it). There are many adjustments you can do to the carb that may fix the problem also.

You have to take the carb off to check the transfer slots, but if the throttle plates are to far open, your idle mixture screws don't really work. If the 850 has only front idle screws and the front plates are opening up the slots all the way to make it idle, then you need to pull the carb and adjust the small screw on the secondaries (on the base plate pointing up) to open the secondaries up more so it will idle higer, then adjust the the front plates back down and adjust the idle screws. It's a little tough to explain, but the results pay off

My engines do the same thing. always idle well on trailer but when in water, seem to die frequently. Makes docking a challenge when restarting engines every 30 seconds. i have adjusted the idle speed screw but dont think i should take it any higher. i will look at adjusting other aspects of the carb (Dom 1050) based on thread suggestions.

You might need more initial timing than it was set for. You probably need more initial/base timing.
A 540ci engine making 588hp should idle easily at 800-850rpms.without any issues.

It could also be carb tuning issue. if you have the idle rpm set up that high, more than likely you are not even running in the idle circuit of the carb.
When the boat goes into the water, the angle changes and the float levels may need to adjusted also.