So I’m new to the jet boating scene and have just finished up my racing engine and got it off the dyno for my boat. 400 cubic inch small block Chevy that made just over 800 hp and spins 9,000 rpm. Someone explain to me what i need to do. On the outlet of the pump do i put a regulator to control flow of water for temperature? Then where do i put a regulator for water pressure through the block? Need to keep water pressure below 20 psi so I’m not blowing out gaskets. Someone help me. I am also obviously running dry headers. Thanks!

That's a badass mouse, but I would seriously consider putting a gearbox on it.  You will either have to cut the impeller way down or you won't be able to turn it.  If you cut the impeller down that small, I'm afraid that it just won't work right and it definitely won't leave right.  Underdrive a larger impeller.