In reply to Flinticus:
When I lived in Greenock there were 2 choices. Western Ferries and Calmac. Western Ferries were quicker from what I remember and if still operational may be cheaper. They also made crossings in rough weather when Calmac wouldnt. Western Ferries set off a bit outside of Gourock on the road to Inverkip and docked about a mile to the north of Dunoon whereas Calmac went Gourock centre to Dunoon centre if my memory serves me correctly.
It's way quicker than the road.
Post edited at 22:10