The text message arrived with an ominous ping as I drove north through a rugged Scottish valley to catch the next day’s boat to the spectacular, remote island of South Uist.

Because of “technical issues,” my crossing was canceled, wrote the ferry company, and there would be no trip on this route for the next five days. Politely, but firmly, the company’s phone staff also insisted that my trip was a no go.

Until suddenly they changed course. A little later, a call came in offering a different crossing that would add three hours’ drive time to my journey. But at least it was sailing.

Getting to South Uist — 25 miles, or about 40 kilometers as the crow flies, off the coast of northwest Scotland — always required time and a little patience, but now it feels like travel roulette.

In theory, it can be reached on 10 ferry crossings a week, in three hours and 30 minutes. But so frequent is the disruption to the ferry from Mallaig, on the mainland, to Lochboisdale, on South Uist, that hoteliers fume about canceled bookings and islanders fret about missing travel connections or funerals on the mainland.

The underlying cause is the botched renewal of the aging fleet of boats serving around 50 Scottish ports and harbors — a saga routinely referred to as the nation’s “ferry fiasco.”

Blame for expensive failings has been directed at multiple sources: the Scottish government, which owns the ferry company, Caledonian MacBrayne, known as CalMac; the ferry firm itself; other transport authorities; and tardy boat builders.

While many islands have suffered, tempers are particularly frayed on South Uist, population around 1,400, part of the Outer Hebrides island chain. It offers outstanding wildlife, walking and fishing, a slower pace of life, striking — sometimes desolate — scenery, and turquoise seas lapping at white sandy beaches.

But its economy is being “absolutely devastated,” said Stephen Peteranna, 65, the managing director of Isles Hotel Group, with three hotels in the region, one of which would have to close for a week in June, the high season, after a ferry disruption prevented a coach of visitors arriving, prompting another group to cancel.

Mr. Peteranna recalled how one guest checked in only to receive a message from CalMac warning that the afternoon sailing to the mainland would be the last before a four-day stoppage. “He went straight back out to the car and left,” Mr. Peteranna said.

His cousin John Daniel Peteranna, 56, whose company provides renewable energy and services wind turbines, sends staff vehicles on ferries well before they are required to ensure they arrive when needed. But it is the psychological toll he resents.

“The mental pressure that puts on you is really bad for everybody’s health,” he said. Even the dog senses the anxiety as a family trip approaches and acts out, he added.

South Uist is 200 miles from Edinburgh, the seat of Scotland’s government, but it feels farther. The island has only a few restaurants and little nightlife, but offers dark skies ideal for stargazing. There is a British military base and renewable energy firms, but also tenant farming, known as crofting. Scottish Gaelic is widely spoken.

Residents see the ferry debacle as evidence that they have long been ignored by the mainland. They note that when ferries break down elsewhere, the boat to South Uist is often sent as a substitute, aggravating islanders.

“You can’t help over the years but to feel victimized for where we live,” said Olivia MacLellan, 49, who works in community programs for alcohol and drug recovery, as well as horticulture.

The Scottish government acknowledges the problem and has opened a 4.4 million pound fund, or about $6 million, to compensate communities worst hit by the ferry disruptions, including hotels, cafes and other businesses.

CalMac’s vessels are on average 24 years old, and one-third of them are beyond their life expectancies. Those showing their age include the 36-year-old MV Lord of the Isles — known affectionately as “Loti” — which operates the Mallaig to Lochboisdale route.

My outbound trip on Loti was canceled after the discovery of a small hole in its hull. (It was repaired in time for the return.) Last year, Loti was diverted after a fire broke out in its engine room, recalled Roderick MacKinnon, 67, who had to scramble for overnight accommodation along with other passengers.

With Loti out of service, I was diverted to the main alternative route, which is shorter at sea, but meant far more driving. (The ferry crosses from Uig, on the Isle of Skye, a two-hour drive north from Mallaig, and arrives in Lochmaddy, in North Uist. Then it’s another hour’s drive from Lochboisdale along a road that in some places is only one lane.)

After listening to a performance of bagpipe music and Gaelic songs in Daliburgh, South Uist, Marie Campbell, 77, said the disruptions had cast a cloud over a looming family trip to the mainland to celebrate her son’s 40th birthday.

“Do we go the night before and book another night’s accommodation?” she asked — a precaution requiring some relatives to take a second day off work.

On South Uist, she said, “We don’t say, ‘We are going on Friday.’ We say, ‘We are going on Friday, hopefully.’”

Rupert Marshall, an author who runs a bed-and-breakfast on South Uist, bought tickets on both ferry routes, just in case, for an upcoming trip in September.

Mr. Marshall looks enviously a few hundred miles north, to the Faroe Islands, a self-governing archipelago that is part of Denmark, where a network of tunnel connections includes an undersea roundabout. Here in South Uist, he recently lost around £1,000 ($1,350) in bookings, equivalent to a month’s mortgage payment, when the ferry stopped running.

Yet there was praise for CalMac from Roddy MacDonald, 72, who farms 18 acres of land — like his father and grandfather. He applauded the special sailings that get animals to the mainland to coincide with auctions.

But human passengers have no certainty, and Mr. MacDonald was unsure he would reach a weekend memorial service on the mainland.

The most vivid symbol of Scottish ferry dysfunction is the Glen Rosa, moored on the River Clyde outside Glasgow. It is still under construction seven years after its original completion date at triple the original price tag for this and one other vessel.

Graeme Thomson, the chief executive of the ship’s builders, Ferguson Marine, promises the Glen Rosa will be ready by mid-2026. He said he was “profusely apologetic to the islanders.”

There were more apologies from Duncan Mackison, CalMac’s chief executive, who believes the disruptions will most likely persist until newer ferries arrive — some are being built in Turkey.

CalMac is “often in crisis management mode and that is likely to continue for a number of years until we get the age of the fleet down,” he said. “We just need to get through the next year to two years without shooting each other.”

That may not placate islanders who in 2023 staged a demonstration in Lochboisdale harbor and now have a new weapon in their battle with the ferry firm — a protest song with a jaunty chorus: