A former security guard has been sentenced to life plus 85 years in prison for the 2007 hijacking of the "Joe Cool" charter boat and killings of four people aboard.

U.S. District Judge Paul Huck imposed the sentence Wednesday on 21-year-old Guillermo Zarabozo, who maintains his innocence.

Zarabozo was convicted in February of 16 charges including kidnapping and murder, which carries a mandatory life sentence.

Already serving a life prison sentence is 37-year-old Kirby Archer, who pleaded guilty.

Prosecutors said Archer and Zarabozo chartered the boat intending to hijack it to Cuba, then fatally shot the captain, his wife and two crew members while at sea.

Zarabozo claims Archer committed all the killings, but a jury found otherwise.