2003 VMAX 150 water pressure?

It has been awhile since I ran my boat and I cant remember if this is right. When the motor is running and not in gear the water pressure gauge shows about 5 psi then when running at mid range it shows about 13 psi and at wide open it shows about 20 psi is this normal? When I take off and slow down the pressure gauge acts almost as fast as the tach.

Thats normal.

Alot to do with summer water temp.