The four men from Latvia and Lithuania were intercepted by the French navy off Tonga in July.
The skipper was jailed for seven years and the three others for six years.
The defence asked for their acquittal.
They said they didn't know about the drugs, claiming they were paid just over $US2,000 a month for sailing the yacht for refurbishment in Australia.
According to the Nouvelles Caledoniennes, one of the convicts is an 18 year-old who was encouraged by his father to take the job in order to be able to go abroad for the first time.