While the "Cat" fast ferry is an interesting trip, don't look at it as a way to save time. For $99 USD (plus $10 "port fee") per person and another $101 for your motorcycle, you can arrive at the ferry in Bar Harbor a minimum of an hour before the 3 PM sailing. 3.5 hour passage, probably a half hour (likely more) to disembark and clear customs and then a 2.5 hour ride to Mahone Bay (Shore Cycle). Call it 7 to 7.5 hours minimum, assuming you were already in the immediate vicinity of Bar Harbor. This is compared to an 8 hour highway ride and two tanks of gas from Bar Harbor to Mahone Bay. Also, the boat lands in Yarmouth ~7:30 PM (local time - you lose an hour time difference from ME to NS) so it would be at least 10:00 PM before you could get to Mahone Bay - certainly after dark. I guess you could get a hotel in Yarmouth and head out EARLY in the morning - hotels are likely booked well in advance if the ferry is running. Timing works a little better for the trip back - leaves 9:30 AM from Yarmouth. All academic since the ferry won't be running anyway.
Same deal with the ferry from Saint John to Digby - not much, if any, time savings and there is significant cost.
I would like to get there but not sure I can manage it! Will know better in a few days. (I would likely get to Halifax Friday night and stay with friends and head out for an hour's ride (2 hr if I take the very scenic coastal route) to Shore Cycle Saturday AM.)