I am also constructing a small boat as a test bed for a much larger houseboat. If we forget about practicality issues.... and accepting that my BS econ degree from the 60's isn't helping me much, I have a simple question with a difficult answer I guess. 2 stage centrifugal pump. (Standard purchase) 7.5hp. 100m³hr flow rate. 4 inch inlet. 4 inch outlet. ~50 psi. 0 to 3500rpm variable... If I restrict the output with a fixed nozzle of, say, 2 inches, will I get the needed increase in velocity without stalling the pump or causing cavitation in the pump? Of course there are a lot of othere related questions. Learning here is as important as the answer.... And, please, no boat forums. They know less than I do but don't realize it.