Check my thread, this is how I will do it.
1st day - Drive to Portland, arrived at afternoon, eat at eventide or Street & co
2nd day - Portland - Portland head light house, Casco bay line ferry
3rd day - Go to Bar harbor using route 1 and route 3, visit Mt Battie & Rockland breakwater light house
4th day - Bar harbor, Cadillac Mt, Jordan's pond - go home.