PASSENGERS are facing further disruption on one of Scotland's busiest ferry routes after a vessel that should have been phased out suffered engine problems.

Investigations and repairs are underway to MV Caledonian Isles' starboard main engine.

The issues, believed to be the result of an air leak in the engine of the 29-year-old vessel, have caused cancellations on the busy Ardrossan to Brodick route.

It comes a month after police had to be called to deal with “aggressive behaviour” by passengers who faced a weekend of ferry disruption hitting one of the busiest days on Arran after another problem with the vessel.

Some drivers had to embark on a 125-mile detour after issues with the vessel surfaced at the start of August as Arran hosted the Brodick Highland Games.

Then, it had suffered a problem with a main engine water cooler before creel ropes became caught in its propellers.

The vessel, one of the biggest in Calmac's fleet, was also out of action for more than two weeks at the start of the tourist season in mid-April when a port main engine failure combined with a gust of wind made it hit a harbour wall.

Last September a problem with the sewage system meant it was withdrawn from service to undergo repair leading to more ferry cancellations on the route.

CalMac says the second vessel on the Brodick route, MV Isle of Arran is continuing to operate and there were hopes of a fix by Wednesday evening.

Caledonian Isles was due to have been replaced by Glen Sannox one of two much-delayed vessels still languishing at the Inverclyde shipyard of nationalised Ferguson Marine.

Glen Sannox and its sister ferry Hull 802, which are needed to help begin to replace an ageing fleet, is running at least five years late with costs escalating to at least two-and-a-half times the original budget.

Issues with building the ferries mean that Glen Sannox will not see service till between March and May 2023 at the earliest, while Hull 802 is not due to set sail till between October and December 2023.

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A CalMac spokesman said: “MV Caledonian Isles is currently alongside at Brodick and has developed an issue with an air leak.

“Repairs are underway and hope to be completed by this evening.

"Two return sailings have been cancelled but the other vessel continues to operate an Ardrossan-Brodick-Ardrossan service.

"There are also sailings on the Lochranza-Claonaig route on the other side of Arran.”

It is the latest in a series of issues with the ageing CalMac vessels.

Lifeline services to Skye were cancelled as another of CalMac's oldest vessels, which is due to be phased out, suffered engine problems.

Services on the Mallaig to Armadale on Skye were cancelled as the 31-year-old MV Loch Fyne suffered issues with the overheating of a forward engine.

After a repair was carried out, the vessel was to return briefly yesterday, only for Calmac to find that issue had "recurred" and further services had to be cancelled.

Some 17 of CalMac's 31 working ferries deployed in Scotland are now over 25 years old.

After 1973, when the Caledonian Steam Packet Co. acquired most of the ferries and routes and began joint Clyde and West Highland operations under the new name of Caledonian MacBrayne, the official expected life of a ferry had been 20 years.

That is until 2002, three years after the 1999 devolution when the then Scottish Government-owned Caledonian MacBrayne which then owned the fleet and procured vessels, extended the 'working life' from 20 years to 25 years.

Last month, calls were made for a Scottish Government summit over a ferries crisis which had been linked to food rationing in shops on Scottish islands and people sleeping in their cars.

The MV Hebrides was sidelined after it required repairs to its firefighting system meaning two key Outer Hebrides routes were out of action for three days, while several other key Western Isles routes suffered major disruption last week, with the MV Isle of Mull being redeployed from Mull to cover the shortfall.

Twenty-two-year-old MV Hebrides had been taken out of service for a third time in a matter of weeks causing a shutdown of the routes between Uig on Skye, Lochmaddy on North Uist and Tarbert on Harris.

Islanders complained of food shortages, restaurants struggling to get supplies, visitors sleeping in cars and village halls and visitors re-routed on lengthy detours.

Islanders were concerned it led to rationing of basic items such as bread and milk.

CalMac denied that the disruption was the cause of the supplies shortages.