I use my phone a lot 2,500 min a month I travel all of Michigan, Ohio, Kentucky, Indiana and Illinois. The only phone I have ever used that covered all of the areas believe it or not is Nextel. The only service I have ever found with unlimited any time minutes is Nextel (Grandfathered in @$149.00 per Month). The kids use Cricket unlimited at around $35.00 per month.
The two-way works out great for us, most of the dock hands have it and makes it easy coming in to find out what side of the boat to start prepping first.
This works out great for us but may suck in other areas for others, since we seem to boat in the same waters hope this helps.
BTW don't you need a boat first before you can use a phone on it
Sorry someone had to say it