The Marina Baru 2B, carrying 118 passengers and crewmen, sank in the Gulf of Bone on Saturday while on its way from Kolaka in Southeast Sulawesi province to Siwa town in South Sulawesi province.
The head of the local disaster mitigation agency, Alamsyah, revised the number of survivors on Thursday to 40, saying one person had been counted twice.
Boats are a common form of transportation in the world's largest archipelago nation, which spans more than 17,000 islands with a population of 256 million.