There have been several posts on the forum recently about reaching Islay, and a perceived need to go there by car from elsewhere in Scotland, with a fairly long journey.
The ferries run from Kennacraig on Kintyre- about a two and half hour drive from Glasgow, or a slower and scenic route by driving the M8 to Gourock (45 minutes, 60 to be generous), then Western Ferries every 20 minutes to Dunoon Hunters Quay, drive across Cowal to Portavadie (60 minutes), hourly ferry to Tarbert (Loch Fyne) then a short ten minute drive to Kennacraig. That route also breaks up the journey nicely.
Also a Citylink bus from Glasgow connects with all daytime ferries.
If you are arriving from Arran you drive to Lochranza, take the ferry to Claonaig (sometimes Tarbert, Loch Fyne) then a ten minute drive. Twice a day a bus on Arran and a bus on Kintyre also link the ferry with the two ports, so that is also easy.
There are also twice daily flights from Glasgow Airport with Loganair. Like all Scottish domestic flights the size of aircraft (and thus the relatively low flying altitude) means that the flights are tremendously scenic, and you appreciate the country from a totally new perspective. Those flights (due to their size) have just a 40 minute check in at both airports.
There is also a ferry to and from Oban twice a week in Summer (Wednesday and Saturday) via the island of Colonsay (serves Port Askaig)
Last but not least there is a passenger ferry from Ballycastle (Northern Ireland) to Port Ellen on Fridays to Mondays April to September) in just 75 minutes- daily (twice daily late May to end August)- https://kintyreexpress.com/
So a unique way to travel from Northern Ireland to Scotland in a day or with an overnight/multi night stopover.
Once on Islay there is a surprisingly comprehensive bus service (which serves the airport and both ferry ports).
But there are also no less than ten taxi companies and two car rental companies. They serve the airport, and both ferry ports with one way rentals on island available. For North Americans they will only rent automatics, not stick shift
Islay Car Hire
Cresswell Cars
A couple of the taxi companies will also do bespoke island tours if asked, as the island is more than Whiskey- nine distilleries including the newest at Ardnahoe.