Auckland academic David Wright says he has solved one of the great marine mysteries of the Pacific Islands -- the 1955 disappearance of the MV Joyita's passengers and crew.

For nearly 47 years, the loss of the 25 people on Joyita, including a number of New Zealanders, on a 300 nautical mile voyage from Apia in Samoa to the Tokelau islands has remained a Mary Celeste-type marine mystery.

But the disappearance has always been a family story for Wright, whose mother's cousin Roger Pearless -- the New Zealand administrator in Tokelau -- was one of those who went missing.

Now an English lecturer at Auckland University, Wright has compiled years of research on the vessel and its occupants and plans to publish a book on the mystery next month.

And in the manner of mystery writers, he doesn't want to give away the solution -- at least until the book is published.

But Wright said today he had been able to refute a number of the more outlandish theories which kept the hunt for the missing vessel in headlines around the Pacific for months.

Two of the headline-grabbers he has sunk include the proposition that the vessel's occupants were kidnapped to the Soviet Union by a Russian submarine, or slaughtered by crew from a Japanese fishing fleet.

And he has also discounted two or three sightings -- after the disappearance -- of Joyita's captain, Dusty Miller, in Singapore, the West Indies and Honolulu.

"None of them were substantiated and I don't believe he survived the disappearance," Wright said.

Wright's theory -- yet to be detailed publicly -- is simple and terribly tragic: he says there is evidence that the boat was taking water leaking from a corroded pipe in the engine cooling system for a long time before anyone noticed.

"All of the expert witnesses at the inquiry assumed that the boat became flooded because that pipe broke," he said.

While it was disabled and taking water at night its occupants abandoned ship in tiny rafts, or "carley floats".

Someone incorrectly believed they had sent out a mayday signal on a radio -- which was actually not working -- and "persuaded" the crew and unofficial passengers to wait on the rafts for rescue by a Royal New Zealand Air Force Sunderland flying boat that never arrived.

One by one they would then have drowned -- there were only a few lifejackets aboard -- or been killed by sharks.

Important clues to the "abandon ship" scenario include that the chronometer and log book were taken, along with a couple of firearms Miller kept aboard. Wright believes the firearms may have played a key role in forcing Miller off a wooden vessel he personally regarded as "unsinkable".

When Joyita was found, enough fuel had been used to take the boat 243 miles -- it was probably abandoned within 50 miles of Tokelau. The leak probably started after 9pm on the second night of the voyage -- with nine hours of darkness ahead of them.

"If whatever went wrong, had gone wrong in daylight, I think the outcome could have been quite different," Wright said. Instead, somebody "transmitted" an emergency message, and then put everybody -- including the captain -- overboard on the floats.

The captain knew the radio was not transmitting, but did not realise the aerial fault could have been fixed with a few centimetres of wire.

"My belief is that they had thought they had sent a distress message, which made it more logical to climb onto the tiny rafts," Wright said.

"They certainly didn't get off the boat in a bid to reach Tokelau."

Joyita never arrived at its destination, no distress message was received from it, and an extensive search by the Royal New Zealand Air Force failed to find any sign of it.

The 23m Joyita turned up -- listing but still afloat -- drifting north of the Fiji island of Vanua Levu, 37 days after starting its two-day run to Tokelau on October 3, 1955.

When found by a passing cargo ship, Joyita had drifted 1000km from its scheduled route.

A Commission of Inquiry investigated the case -- with the help of a young lawyer later to become a Chief Justice of New Zealand, Sir Ronald Davison -- but the commissioners reported the fate of the passengers and crew as inexplicable.

"The evidence that the commission of inquiry heard ought to have been sufficient for them to have been able to resolve the whole case -- and it remains a puzzle why they didn't," Wright said.

He said today his own careful reconstruction of the ill-fated voyage revealed the explanation for the tragedy, which will be revealed when his book, Joyita: Solving the Mystery is launched in Auckland, on April 9, by ethnographer Judith Huntsman, an expert on the people of Tokelau.

Six men, women and children returning to Tokelau, including a family of four, were among those who died.