Youth with a Mission Ships Aotearoa sails to remote Fijian islands to provide free healthcare, but Koha is currently at a standstill because of a broken tailshaft bearing.
Managing director Marty Emmett told Morning Report the vessel was specially equipped with two on-board dental clinics and other medical equipment.
He said more than 5000 people living in isolated islands in Fiji had benefited from the ship in the past two years.
"We've been all around the Maritime Islands in Fiji this year...We're really focused on isolated villages where they can't access the basic services.
In order to access basic dental and optometry services, locals would otherwise have had to travel quite far, Emmett said, something which was prohibitive in time and costs for many.
The ship, struck with a NZ$300,000 bill, now needs to be dry docked and repaired.
Emmett said the organisation could pay $100,000 but needs $200,000 in donations to cover the rest.