You need to find out what the gross trailer weight of you boat is with all hardware and full of fuel. Then find out the towing capacity of your Explorer. You should be able to find this out in your owners manual. If not, call a Ford dealer for help.
I would take a serious look at the wheel base of the Explorer myself. Probably wouldn't be my first choice. If you are towing for VERY short distances you may be OK. We used to have a Chevy Blazer, I wouldn't have considered it with that. IMO
Keep in mind, you need to be able to stop more importantly then getting the boat moving. Any quick movement of the steering wheel to avoid something on that short wheel base could get ugly.
The Expedition would get my vote before the Explorer.