Implemented correctly the boat could be a very good idea. As long as they stay within sight of the coast and use the motor sparingly, they could have a great escape vehicle. I'd prefer for them to go up and down the coast scavenging for supplies, or stop at an area that they think might be safe and stay there. They'd always have the boat for a quick getaway, but live on land and use the boat sparingly. Kenny at least knows the waters around Florida, and probably a few small port towns they could camp outside of and raid for supplies when they needed to.
But actually living on the boat would be a terrible idea. It can't hold many people or supplies and fuel would be harder to find as time goes on. The boat is less of a permanent solution than it is an ace in the hole for when things get too rough where the group is staying.