If that's at WOT, then that would be low. I don't know the specific readings for your engine though. Something around 20 PSI would probably be close at full throttle..
4-5 psi at idle and 14 - 17 psi at wide open throttle. No two engines are the same so the idea is to install a new water pump. Note the idle and and WOT pressures. Any deviation from those numbers in the future indicates the impeller is in need of replacement again.
