The youth carried a crowbar. His associates had a hammer and a knife.
One held a knife to the barman's chest and made him open the till and a locked cupboard. They got away with $10,155.60.
"The majority of the money was spent within 24 hours on cars and alcohol," the judge said.
About 7.35pm on July 10, Huta and Karaitiana returned to the tavern armed with a crowbar, making off with $435, which was spent a short time later.
In his victim impact statement the barman said he feared for his life and had since given up his job fearing another robbery.
Judge McGuire said the pre-sentence reports for Huta and Karaitiana were "bleak".
Both had a number of previous convictions and Huta was just two months into a sentence of intensive supervision at the time of the robberies.
Judge McGuire said the 16-year-old had been doing well on remand at a youth justice facility, showing leadership skills and a talent for music.
"If you prefer the gang [life] well you might as well tell me right now and I will save my breath," the judge told him. "That ain't much of a life."
A fourth man, Horima Tamati, was previously jailed for five years for the first Westbrook Tavern robbery.