More than £55million is to be invested in new piers and infrastructure at three harbours serving Western Isles communities.
But the race is on if the critical element of construction work is complete before a new £49million ferry starts on the Skye-North Uist-Harris triangle route next autumn.
As part of a public consultation display boards showing the building plans are on show in ticket offices at each port this week.
The unnamed vessel – being built at Ferguson’s yard on the Clyde – is expected to take over from the MV Hebrides in September 2018.
With a bigger mass the more powerful ferry would put extra strain on the aging piers during berthing – particularly in bad weather – so each harbour is being upgraded.
At each location, the seabed will be dredged to allow more room under the hull while part of the shore will be filled in and tarred to create bigger waiting and marshalling areas for vehicles.
All piers are being rebuilt, lengthened and strengthened to cope with the larger boat.
Scottish Government agency Caledonian Maritime Assets Limited (Cmal), which will lease the ferry to Cal Mac, also owns Tarbert harbour which will cost £13.7million to reconstruct.
Lochmaddy upgrades proposed by owners Western Isles Council would be about £15.3 million.
Highland Council intends to invest £26.5million to improve the harbour it owns in Skye.
Lorna Spencer, director of harbours at CMAL said: “No final decisions have been made on what work will be carried out.
“In addition, the proposals are subject to funding availability.”
Recent public exhibitions attracted a good turnout and “we will take on board the feedback we have received and use it to inform the ongoing planning process.”