Officials said Saturday eight people were confirmed dead, including at least two children.
Investigators say about 50 people were on the vessel Friday, traveling from the capital, Conakry, to an island off the west African coast.
Some passengers on the ill-fated vessel were rescued, but a rescue official is quoted as saying that hopes of finding survivors have faded, meaning about 30 people could be dead.
One survivor says the boat experienced engine trouble before it overturned Friday night.
Crowds gathered on shore where some of the survivors were brought to safety.
Accidents on overcrowded boats that are poorly maintained are common in the region.
In recent months dozens of people of have died in boating accidents off the West African coast.
Some information for this report was provided by AP, AFP and Reuters.
