TWO of CalMac's 14 major vessels serving some of Scotland's busiest lifeline island routes are sidelined to passengers as severe disruption hits the network.

Concerns have been raised about disruption being felt across the network as the depleted ageing fleet is redeployed to try and cope with the loss of both 38-year-old MV Hebridean Isles and 30-year-old MV Caldeonian Isles to passengers.

MV Hebridean Isles first hit problems on Boxing Day and has been on and off service with bow  visor issues while serving passengers to Arran with MV Isle of Arran.  A bow visor is a feature of some ferries that allows access to the cargo ramp and storage deck.

It ended up as freight-only service to the island two weeks ago but has been suspended since Wednesday because of another issue being worked on by engineers. It is unclear when it will return to providing normal passenger services.

It had been expected to support services to and from Islay with the MV Isle of Arran for an overhaul for two months from this Saturday as part of the rejigging of the network through the state-owned service's programme to improve fleet sustainability through its overhaul programme.

But it appears neither vessel will be able to make it.

CalMac have decided to cut the Islay service to a single vessel and drafted in MV Finlaggan until February 16. But it was supposed to provide services for a month from next Monday to and from North Uist through a temporary timetable brought in by the closure of Skye's Uig harbour for essential repairs.

MV Isle of Arran has been serving Arran for weeks on its own because of the issues with Hebridean Isles, cutting the number of available vehicle spaces to about half. It is expected to remain solo till at least February 16.

Meanwhile, issues discovered with engines, including a turbocharger rotor and bearings and steelwork has meant the return to service of 30-year-old MV Caledonian Isles could be delayed for up to five weeks.

The vessel was originally withdrawn from the Ardrossan-Brodick route for annual maintenance.

The launch of MV Hebridean Isles in Selby, Yorkshire

According to CalMac the overhaul was due to conclude on Friday after being in dry dock for nearly a month with more than £1m of scheduled work being done to the vessel, including engine servicing.

But the inspections uncovered further issues including damage to both engines with the estimate for a return at three to five weeks.

The vessel, which carries 1000 passengers and 110 cars, was out for weeks just last Easter due to an engine failure.

Before the new year a third of the 14 major vessels 35-year-old MV Isle of Mull was found to have suffered hull rust issues and subsequently engine issues and was sidelined for weeks.

It was to emerge from its month-long annual overhaul on December 23 but remained out of action nearly three weeks later.

An economic study commissioned by North Ayrshire Council found that disrupted ferries cost the Isle of Arran up to £170,000 a day in lost revenue to businesses.

One ferry user group official said: "The knock on effects of this chaotic situation are not just being felt in Arran but across the network as vessels don't seem to know whether they are coming or going through all the juggling. It is insane. You just cannot have a situation where there are two key ferries out and insufficient cover. I do not envy CalMac having to solve these puzzles but suggesting that these vessels can serve the public for longer than they are actually capable is folly.

"This is all the result of a failure to replace our fleet not just long term, but short term and a failure to provide adequate capacity even on a short term basis is just criminal and it is islanders that suffer."

Some 18 of of CalMac's 35 working ferries deployed across Scotland are now over 25 years old.

The oldest in the CalMac fleet is is the Isle of Cumbrae which is 47-years old.

Two new lifeline ferries Glen Sannox and Hull 802 were due online in the first half of 2018 when Ferguson Marine was under the control of tycoon Jim McColl, with one intitially to serve Arran and the other to serve the Skye triangle routes to North Uist and Harris, but they are at least five years late. The last estimates suggested the costs of delivery were due to soar from £97m to at least £350m.

In 2021 the state-controlled ferry operator spent more than £28.5m on repairs to their vessels last year, compared with just £9.5m in 2011.

An aerial video of MV Caledonian Isles.

Since the SNP came to power in 2007, the average age of Scotland's lifeline vessels has soared from 17 years to nearly 26 years. Back in 1974 the typical ferry was just 13 years old.

A CalMac spokeswoman said: “Due to MV Caledonian Isles now requiring additional engine and steel work during her annual overhaul period, the vessel will be delayed in returning to service. As a result of this, it has been necessary to amend the network vessel deployment plan.

"We are sorry for any disruption this will cause to communities and we are working hard to ensure that any inconvenience is kept to a minimum.

“Our initial deployment plans will be in operation until 16 February and are available to customers on our service update pages on our website. These will be regularly reviewed and updated for the period beyond.”

CalMac said a "unique component" that is critical to the safe operation of the bow visor of MV Hebridean Isles needs to be fabricated.

The ferry operators said that detailed design drawings and modelling work continue and soon as this has been completed, and  new component is tested, works will then start on the vessel itself, to enable the bow visor to once again be safely and fully used.

When the issues first surfaced with MV Hebridean Isles during the festive period, itwas withdrawn from the busy Arran route to undergo repairs to a bow visor seal.

Further issues were registered three days later and in January 3 it was withdrawn whle MV Caledonian Isles was offline for an annual overhaul, limiting islanders to a one vessel service.

Five days later after repairs were complete, it remained sidelined due to a new issue with the bow visor locking mechanism.

By January 10 MV Catriona was shifted from the Tarbert to Portavadie to provide support on the service to Arran's other port Lochranza. User groups say that led to suspension of services between Tarbert on Kintyre and Portavadie on the Cowal peninsula for nearly a week starting on January 6.

On January 10, it remained out of action due to what CalMac called an ongoing issue with a bow visor hook.