The council has been setting sea trials for its Sullom Voe tugs Solan and Bonxie in the hope well-documented steering problems can finally be banished.
However it remains unclear how long the tugs – which cost the authority £7 million each – will remain in council ownership.
The SIC is examining the possibility of selling off the Spanish-built vessels. Doing so could help the authority recoup at least some of the costs which have mounted during the long-running debacle.
Chairwoman of the SIC’s harbour board, Andrea Manson, says the council may have to examine the possibility of replacing all its tugs.
That is because of the longer than expected life of the oil and gas sector off Shetland.
She highlighted findings which showed the industry in the isles could remain active until around 2050.
“When you’re speaking about 2040/2050, you’re looking at another 30-odd years.
“Within that 30 years all the tugs that we have would become, probably, too old to use – because some of the oldest ones we have now are in excess of 30 years old.
“We need to have a general overview of what we’re going to do with them.”
Moves have already been made to revisit a previous decision to cut the number of tugs from four to three.
The thinking behind buying the Bonxie and Solan was to acquire two larger vessels with a greater bollard pull than previous, smaller tugs.
But the environmental disaster in the Gulf of Mexico shifted the focus back on the need for greater environmental protection.
“The whole idea was to get two big tugs to replace three peerie ones. Since then Deepwater Horizon happened in the Gulf of Mexico. So the oil industry … has far more emphasis
on marine safety.”
She added the Solan and Bonxie may prove too big and “gutsy” if the port is to retain a greater number of tugs.
“Going back to a four tug option, we’ll have to decide whether the ones we have now are maybe too big, too powerful and too expensive to run, and it would be better having four smaller ones than two big ones.
“They have big engines and cost considerably more to run than the smaller old ones do. You don’t want something big and gutsy if you can get off with four smaller-engined vessels.”
She added talks would take place between the council and oil industry representatives.
At 40 metres and with a bollard pull of 70 tonnes, the Solan and Bonxie were the largest and most powerful tugs ever at the terminal.
But crews complained they could not steer in a straight line and in December 2011 they were taken out of service – months after being introduced.
Along with steering problems there were issues with stability, exhaust systems, winches and the handling ability of the vessels.
Both had fins fitted at a dry dock in Leith to correct steering issues.