the boat starts running 30min before scheduled opening but I think that is 30min before EMH. The monorail starts running at 7am every morning. I was just at Poly and was concerned how to get to a 8:10am ressie. It wasn't EMH so we took the monorail. I guess it all depends on where you stay on the resort - which one you are closest too. Also, the monorail only runs every 15-20min or so in the early AM but will hold a lot more people then that boat. The boat picks up at GF first. It may seat around 25 people at best. I don't know personally how crowded the dock gets for EMH but one day around 8:45am there wasn't enough room for everyone to get on and some people had to wait for the next one. If you really want to get there before 8am and waiting at the gate, I recommend heading to the monorail no later then 7:30am
HTH