A teenager from the Papuan island of Bougainville has been found alive about 2,000 kilometres from home after spending 41 days adrift at sea during a fishing trip which claimed his cousin's life.

Luka Rahan, 18, was rescued by Kiribati fishermen on Tuesday afternoon after they spotted his boat between Tarawa and Maiana.

He was alone and severely dehydrated when found, and was taken to hospital in Tarawa, Kiribati's capital.

Mr Rahan had set out from northern Bougainville with his cousin last month, but problems with their boat's motor left them drifting without an anchor.

The ABC reported his cousin died at sea the week before the rescue.

Papua New Guinean engineer Jonathan Anthony Kunau visited Mr Rahan in hospital and helped translate for authorities and healthcare workers.

Mr Kunau said he wanted to help the teenager feel supported while away from home.

"He's from my country," he told the ABC.

"I need to be there for him; make him to feel at home, at ease."

The rescue comes a month after three other Bougainville residents were found near Kiribati following more than two months at sea.

National Indigenous Times reported in September that three Bouganville residents had been rescues after about 70 days at sea when their boat ran out of fuel between Nissas Island and Buka.

They were taken to Kiribati for treatment and returned to Port Moresby on Monday, according to The National.

Mr Kunau said Mr Rahan was responsive and regaining strength, and his family had been informed.

He urged fishermen to carry a compass, anchor and phone with them.