The math says 3hp should get you 4.38gpm @ 1000psi or 3.65gpm @ 1200psi. With 5hp its 7.3gpm @ 1000psi or 6.08gpm @ 1200psi. With my 2506 nozzles at 1200psi I should be using ~3.29gpm and ~2.7hp. So mathematically 3hp would work. The 516 pump is rated from 4-5 gpm depending on the pump rpm. My pumps are spinning at 950rpm (4gpm) and with my 5hp I should be able to pump up to ~1825psi with my 2506 nozzles to max out my set up.