Four men, part of a group dubbed “tinnie terrorists”, have been jailed for their roles in a plot to sail a fishing boat from northern Australia to help overthrow the Philippines government.

But one of the men could be freed within days, a Melbourne court said on Friday.

Two other Melbourne men will be sentenced in the coming months after admitting to their parts in the 2016 plot.

Murat Kaya, now 28, has spent more than 1,000 days in custody over plans for five men to sail to the southern Philippines in a small fishing vessel.

He was arrested during terror raids in Melbourne in May 2016, shortly after the arrest of his younger brother Kadir Kaya, associates Paul James Dacre, Antonio Alfio Granata, Shayden Jamil Thorne and ringleader Robert “Musa” Cerantonio.

They were picked up by the Australian federal police while driving near Cairns, towing a seven-metre fishing boat they intended to sail from Cape York in what the supreme court justice Michael Croucher on Friday predicted would have been a “doomed voyage”.

Murat Kaya had originally intended to travel with them, but pulled out later and was not part of the plans the men had for their wives and children to eventually join them.

All the six pleaded guilty to a charge of engaging in conduct in preparation for incursions into foreign countries for the purpose of engaging in hostile activities, aiming to overthrow the Philippines government.

Murat Kaya was sentenced to a maximum three years and eight months behind bars while Dacre, 33, Granata, 28, and Kadir Kaya, 24, were sentenced to four years with a three-year non-parole period.

Justice Croucher said he believed allowing their release on parole at the earliest possible opportunity would foster their rehabilitation.

If the attorney-general supports that view, Murat Kaya could be released as early as February 27 – next Wednesday – and Dacre, Granata and Kadir Kaya from 10 May this year.

Thorne was the last to plead guilty, on Friday morning, meaning the previous confessions of his co-conspirators could be made public. He is due to face a pre-sentence plea hearing next week.

Cerantonio, described by Justice Croucher as the “charismatic and persuasive” ringleader, will face a plea hearing in March.