IT'S so sunny on Arran that Michael Higgins can't see the picture on his phone.

The 50-year-old heating engineer has been trying to tell how little he thinks of the ferry service to his island. Now he has decided to show it instead.

So he ushers us in the shade behind his white van and brandishes a photo of the empty car deck of an ageing ro-ro. "They had told us the boat was fully booked," he says. "But it was empty. Computer problems."

Mr Higgins is having a picnic lunch on the front at Brodick, Arran's main port, as another load of tourists in sunglasses, their faces glowing red from sun and sea, trundle hand luggage along its promenade. "I like to get off the island when the visitors come," he smiles, watching them. "That is not always easy. In the summer you have to book three weeks in advance."

It is a brilliant September day, the Firth of Clyde is a flat azure that melts seamlessly in to the sky and Arran is heaving. It has been all season. So are the boats that provide its lifeline links to the mainland. The island is home to just over 5,000 people. Last year 911,434 passengers were clocked on its two ferry routes. That is 20 per cent more than a decade ago. The figures for cars are rising even faster, by 44 per cent from 2007 to total 229,664 in 2017.

This summer traffic – most of it on what is often a two-boat service out of Ardrossan on the North Ayrshire coast – has grown again.

The passengers Mr Higgins watched had passed through a high-tech adjustable gangway and state-of-the-art terminal ("over-engineered waste-of-money", the plumber grumbles). But they did so after coming off a boat built in 1984, the MV Isle of Arran. And that is a problem.

The vessel, its interior a beige time capsule of sticky seats and retro puggies, has had problems, more specifically this year, propeller pitch control problems. Cue service disruption, and not for the first time.

The old boat was supposed to have been replaced this summer by a new high-tech environmentally friendly vessel called the Glen Sannox. That ship is delayed. Hence the frustration of Mr Higgins and much the rest of Arran.

Yet this local row – albeit affecting Scotland's busiest ferry route – is just one symptom of a much bigger problem, a problem that has been a generation in the making.

Simply put, Scotland's islands are getting record numbers of visitors but the boats and port infrastructure carrying them are old, really old.

There is a mantra in the ferry industry about this crisis. Nobody, insiders insist, is to blame. And nobody, they add, will be able to find a quick fix.

That is because half of the ferries on Clyde and Hebridean routes have seen out their ideal lifespan of 25 years.

The average age of a ship is 22. In the early 1990s, the last time Scotland had a major burst of ferry-building (seven thousand tonnes worth in 1994), the average age was 12. The number, unchecked, has been rising ever since. In fact, it has been a generation since Scotland, one of Europe's most "islandy" nations, was launching enough ferries to sustain its fleet.

The result? Boats break down. And when they break down they are hard to fix. And our islands suffer.

So far this year five ships on Clyde and Hebridean services have been out of service. One, the Hebridean Isles, built 1985, which usually services Islay, has been laid up twice, thanks to damage in rough seas off Tiree and a collision with the harbour at Kennacraig on Kintyre.

Newer ships, such as the MV Clansman, which services the outer Hebrides from Oban, are among those out of action.

Bad things happen at sea; that is to be expected. What counts is whether the entire system – fleet-wide – can cope when they do.

Take Calmac. The biggest operator of ferries runs most services to islands and peninsulas in Western Scotland. It is state-owned. Its ferries are owned by another state owned entity, CMAL, which also owns or leases the boats that, under a separate Northlink franchise, service routes to the Northern Isles of Orkney and Shetland.

Between January and the end of July this year, some 2,326 out of 79,203 Calmac scheduled sailings were cancelled. Of these 327 were for mechanical reasons. Most of the rest were because of bad weather.

The figure for cancellations for problems with the ferries looks low, not least because Calmac will stress that it laid on more than 900 extra sailings to compensate for some of them.

However, a ferry that does not sail is not quite like a bus that does not turn up on time. There are rarely alternatives. And with ferries packed to capacity, alternative travel is not always easily arrangeable.

When a boat breaks down, a replacement has to come from somewhere else. Somebody always loses. Calmac does not have a spare vessel, crewed and fuelled, bobbing about at sea waiting to save the day. Indeed, even if it did have a spare, Calmac could far from guarantee it could use it. Why? Every port has its own pecularities, whether it is an ageing linkspan or unusual tide. This is not a standardised fleet. Most ships and ports are bespoke.

Usually Calmac gets the blame. It is the firm with the name on the side of its ships, with their trademark blue hulls and white superstructures. In fact, the firm, which had to compete to secure its franchise from its own government owners, has been warning about a growing problem with its service for years.

Back in 2010 the company bluntly told the Scottish Government that a new ferry would have to be launched every year just to stand still.

In its submission to that year's ferry review, it said such a drumbeat of production could cut the average age of the fleet from 22 in 2012 to 19.5 in 2022.

Warnings have echoed ever since. In March, Calmac's chief executive, Robbie Drummond, signalled this summer could be tough. He said: "Any issues with a vessel on one part of the network will have knock-on effects for other routes, as boats need to be diverted or deployed elsewhere to keep the lifeline network running.

"Islay has already been adversely affected by such changes this week, with one of the two ferries that normally serve the island needing to be withdrawn to fulfil contractual obligations elsewhere.

"The working life expectancy of a ferry deployed on routes like those on Scotland's western seaboard is around 25 years, so with nearly half of the ferries working these routes already beyond that milestone - and having been used intensively during those years of service - the risk of mechanical failures and breakdown is significant.

"It also takes longer to get older boats back into service when things do go wrong, often due to the difficulty in sourcing parts across Europe."

By May there were more grumbles. Mr Drummond, summoned to Holyrood, spelled out the problems again. He told MSPs: "It remains the case that we have no spare vessels to accommodate this eventuality.

"It was not a minor breakdown; a major vessel has been out for more than two months, and is coming back in for another two weeks while we get back on track.

"There has been a period of major disruption—the worst the company has experienced for eight years. We have tried as best we can to provide the best possible service through that period."

Key stakeholders are not happy. Outer Hebrides Tourism (OHT) reckons it lost £6m from service cancellations after the breakdown of one boat. Ian Fordham, its chairman, this week said: "While the Scottish Government must now invest in CalMac to improve fleet resilience, they should also recompense our local businesses and invest in rebuilding confidence in the Outer Hebrides as a tourist destination after the negative economic impact of this summer's ferry fiasco. This has hit tourism business not just this summer but its future growth too."

It is not as if the Scottish Government is not investing. The current SNP administration has put a cool billion pounds in to ferry services since it came to power in 2007. This includes £97m for two new ferries being built for CMAL at Ferguson Marine in Port Glasgow. The first of these, the MV Glen Sannox, was supposed to go in to service this summer to replace the Isle of Arran but will not start operating until, at current estimates, next summer. A second, now codenamed 802, will run to the Western Isles to help address the OHT's concerns. It isn't convinced. Among its other complaints were that two new ferries were delayed "with nothing else in a build pipeline."

"How they will manage this against the backdrop of traffic and visitor growth to the Outer Hebrides?" it said.

The boom in visitors was not expected. Some put that down to the Scottish Government's flagship "road equivalent tariff" or RET scheme under which a ferry journey should not cost more than a drive. But other factors are at play: the collapse of the pound after the Brexit vote means more tourists from both home and abroad.

Across the Calmac network, the last five years have been busy. Between 2012 and 2017 the number of cars carried grow by 37 per cent to 1.43m per year. Passenger numbers rose 17 per cent to 5.2 million per year.

Joe Cullinane is pleased with that. He leads North Ayrshire Council, which includes key Clyde ferries, including Arran's. "The fleet is too old to meet the demands of RET," he says. "RET is great for the added tourism. But the infrastructure is not ready to cope with RET, our roads, our ports and our ferries."

The RET pressure has been hardest on Mr Cullinane's patch. Tiny Cumbrae, gets more visitors than all of the Western Isles put together. So many, in fact, that there is now routine traffic congestion in the sedate resort town of Largs from where a new hybrid ferry sails. Why? Cars queuing for the hop across the First of Clyde.

The new ferries on order at Ferguson Marine are also hybrids. This vexes some of Scotland's "armchair admirals", the voices berating the decision to invest in new tech, rather than tried and tested conventional ships. The delays to the two new ships have been at least partly put down to the risk of innovation. Some critics have also suggested a quick order could be placed for a cheep-and-cheerful diesel-guzzling chugger in a low-cost shipyard in the Far East. Policy-makers reckon that would just be another stop-gap solution.

The Scottish Goverment quango Transport Scotland asked Calmac and CMAL to look for off-the-shelf boats to buy or lease to fill the gaps. It even suggested that it would pay for them. So couldn't Scotland just pick up a "rustbucket" from the Greek Islands or Norway? No. There are just no vessels out there that would work.

Transport Scotland said it "continued to invest" in new ships and ports. Its experts stress that ferries should not be seen as ships in isolation. They are part of a complex system that includes ports and other transport connections. They have to "fit".

CMAL had no comment. It has its two new delayed ships on order and then will look to get another, for Islay. The future of Scottish ferries - of Scotland's islands - now lies in the hands of a document CMAL published in January. The Vessel Replacement and Deployment Plan or VRDP is a detailed run-down of what boat should go where for years to come. It's very last words should be music to the ears of Scottish islanders and visitors. It says: “Consider the opportunity to develop a medium/large class of major vessel capable of working effectively and efficiently on a number of routes across the network.”

What this means is a move to more standardised vessels for big routes, namely from Oban to Colonsay, Islay, Coll and Tiree; from Mallaig to Lochboisdale in the Western Isles and Armadale on Skye and from Wemyss Bay on the Clyde to Rothesay on Bute. For standardised ships, these ports will have to have standardised or future-proof harbour facilities built. That is big money. But, crucially, it would mean Calmac could reshuffle its fleet far more easily when something goes wrong.

The VRDP did not say when such plans would be considered. Transport Scotland was able to. It's next year. A spokesman said: "The focus of the next vessel procurement will be a new ferry for Islay to replace the MV Hebridean Isles. This will maintain our investment programme, currently focused on the construction of two major vessels for the CMAL fleet and a number of major harbour projects.

"The development of a medium/large class of major vessel will be considered by Transport Scotland, CMAL and CalMac as part of their programme of work. This is intended to get underway next year."

Back on Arran there was more trouble this weekend. The island's other main ferry, the Caledonian Isles, now exactly 25 years old, was cancelled for technical reasons. Islanders are used to this.

Sheila Gilmore, out walking her cockapoo Archie, was philosophical. Arran born and bred, she now runs the local destination marketing bureau, Visit Arran. "It is frustrating when you can't get off the island. We have to get used to that. What we want is to make sure we have two ferries on the main Ardrossan route all year round. Across the network? Resilience is the issue. We need a spare boat."