A propeller has broken on a Cook Strait ferry leased to replace another vessel which lost a propeller.

The mystery of what is happening to Cook Strait ferry propellers has deepened with a broken propeller discovered on a replacement ferry.
KiwiRail still does not know why a propeller fell off the Aratere ferry on November 5 and it is now investigating why part of a propeller blade has broken off its temporary replacement the Stena Alegra.
The state-owned company says crew of the Stena Alegra noticed a mechanical issue when the ferry was at sea on Thursday.
"When the ferry returned to port in Wellington divers discovered part of one of the ships four propeller blades on one propeller was missing," the company said.
Two of Stena Alegra's sailings on Friday have been cancelled as a safety precaution but the company says passengers and crew were not at risk on Thursday as the ferry has two propellers.
Interislander general manager Thomas Davis says safety is a priority and all passengers affected will be offered sailings on alternative ferries.
The Aratere is being repaired in Singapore where cracks were also found on a rudder shaft, delaying its return to New Zealand.
It is due to be back in service by the end of June.
The ferry's breakdown was forecast to cost about $30 million, including lost passenger and commercial revenue and the cost of the replacement ship Stena Alegra, before the latest issues.