A lot of the ferries have room for cars -- but it adds to the cost, and you often need advance reservations to make sure they room for your car. At least that's how Cal-Mac runs; it's easy to do, but it tends to make one fit your golf schedule around the ferry schedule if you're doing a lot of island hopping via ferry with a car. (e.g., you can get from Ardrossan, near Troon and the other Ayrshire links, to the Isle of Arran, and from Arran to the Kintrye Peninsula and on down to Machrihanish, but it won't save you any time -- I'm pretty sure it's quicker just to drive from Troon the long way around to the Kintyre peninsula.)