The old crane at the end of St Peter Port harbour is undergoing major maintenance for the first time in nearly 40 years.
The crane, known as Number 5, has had its jib and counterweights removed.
Guernsey Ports says these have been taken to St Sampsons for shot blasting and painting, to remove corrosion and protect the metal.
The timber on the crane’s cabin is also having replacement planking fitted.
A spokesperson for Guernsey Ports says it's a major operation, and doesn't happen very often:
"The expected work has expanded as more corrosion has been found so it was deemed sensible to deal with this now rather than at a later date. The last time the jib was removed was in 1984, when a similar operation was undertaken, along with works to the operating control system."
Number 5 crane is used to lift inter island cargo. Guernsey Ports says it undergoes regular planned maintenance and independent inspections to enable it to be certified as safe to use.
It is expected to be back in service in June.