We were just there last week and found out that the boat was starting morning trips to MK at 8:30 for a 9am opening. I thought the guest who told me that was wrong so I asked the CM driving the boat and he said it starts at 8:30.
I'm sure it will start earlier for an early morning park opening but not sure if it will be a full hour before opening like the previous poster said.
Just wanted to share our recent experience...
Jennifer