but a good average from MDI is around 12 hours. When I was younger I often made the trip in a day. Now I usually stay at Roque or Cow's yard along the way and make it an easy two day trip. St Andrews is about 5 hours from Roque and Roque is about 7 hours from Southwest Harbor..at least with my boat. You have to watch the tide and the weather. Strong wind against strong tide in the Grand Manan Channel is not fun.