First off, nice chart.... well done.

I am surprised the Tsunami 800 is only putting out 7.5 GPM, they are rated by Atwood for around 14 GPM. I know I am getting better then 7.5 GPM out of my 800's in my setup. With all three 800's running, drafting out of one 3/4" intake, I am getting about 9.5-10GPM per pump, close to 30GPM when running all of them. It takes me about 8-8.5 minutes to fill 1900 lbs of ballast which is about 228 gallons.

Could you possibly get a little more flow from the water pressure coming in from the bottom of the boat when they are mounted well below the draft line??????