The luxury yacht Makayabella was intercepted in September last year after crossing the Atlantic.
David Webster, 44, of Rillmead, Otley, West Yorkshire and Philip McElhone, 29, of Freemantle Place, Halton Moor, Leeds, both appeared via video link at Leeds Crown Court today.
They both pleaded guilty to conspiracy to import Class A drugs between March 1 2014 and September 29 2014.
The two men have been remanded in custody until sentencing in September.
It is believed the drugs, which came from Venezuela, would have had a street value in excess of £160 million.
The Makayabella was intercepted in poor condition by Irish authorities in the Atlantic Ocean, 200 miles off the south-west coast of Ireland, while investigators also seized a 25ft motor boat called Sea Breeze, moored in Pwllheli, north Wales.
Judge Guy Kearl QC said: “Mr McElhone and Mr Webster, you pleaded guilty to these matters. I’m going to adjourn sentencing. In the meantime each of you will be remanded in custody.”