To pump 24 GPM using a single stage pump at 3000 psi, will take about 49 HP.
However, you can run that pump with whatever engine you have until it runs out of HP.
As soon as you get the resistance to cause the pressure to go to 3000, psi, at that point you will need 49 HP.
The pressure that will stall your 24 GPM pump using 18 HP is about 1100 psi.