Check the train timetable at First ScotRail where the Wemyss Bay timetable is "Route 16 Glasgow - Wemyss Bay/Gourock." The Wemyss Bay/Rothesay ferry timetable can be seen on the Caledonian MacBrayne Website, where you can also check the Colintraive/Rhubodach timetable.
Car drivers often enjoy the longer but more scenic drive to Colintraive in Argyll, where the ferry crossing to Rhubodach on Bute takes a mere 5 minutes.
From the ferry terminal in Rothesay turn left and drive along the coast road for just over 1 mile. Just past the Craigmore Tearoom turn right up Albany Road, following the signs for Ardencraig Gardens. Turn left at the top into Crichton Road and where the road bends sharply to the right continue straight on, keeping to the left. This is Ardencraig Road. You will come to a small white lodge house outside the entrance to Ardencraig House. Come up the private driveway and park on the left hand side.