Are there any possible dangers in running a abnormally powerful motorbon a pressure washer pump?

I have a pressure washer pump that is designed for a honda gc160(piece of trash) but i got the washer for free and the cylinder warped so i'm selling the parts out. I'm curious if i put a honda gx200 modified heavily ~10hp as opposed to the 5.5hp gc160 would destroy the pump even if i kept the throttle low.

You have identified one possible "danger", so yes, there are.
There should be safety devices fitted, but if you keep the throttle low you are keeping the power down. But in doing so you may not have the revs to make the pump work…