Sounds like you need more AF in the tank or you left a valve open.
I blow mine out with 55 lbs, including the Water Heater, Toilet and below deck shower, Then I just pour some AF in the drains and All Done- 30 min tops. Also leave all faucets open and wire tie the Spray vales open.
Oh and remove filter from below Kit sink
1992 American Eagle-8.3C-450hp