A Maritime Officer then visited Whatuira and imposed conditions on the yacht, Coriolanus, under the Maritime Transport Act.
The conditions stated that a ship surveyor would have to find the vessel seaworthy before it could be sailed from the harbour.
Four months later, Whatuira was found to have sailed Coriolanus to Westport without adhering to the conditions, and a further nine months later he, and a female companion, had to be assisted to bring the yacht back into harbour in rough conditions.
The judge told Whatuira that he put a passenger and rescuers in danger when using his yacht, and that his conduct was "highly reckless".
"This boatie put his own life and that of others in danger when he ignored Maritime NZ's directions and sailed from Wellington without making the necessary improvements to the old wooden yacht he bought for $500 online," the judge said.
"The engine was not working when conditions were put on this vessel, and the limited equipment on board, such as the sails and rigging, were old and in poor repair.
"The vessel did not have a working radio, any approved lifejackets, charts or other means to navigate."
Maritime NZ central regional compliance manager Michael-Paul Abbott said the conviction was a reminder to all skippers that they must ensure their vessels are properly maintained and fit for a sea journey, and that they must comply with any conditions imposed.
"This man ignored obvious warnings over a more than 12-month period that the yacht was not fit to be sailed, and that he was putting his own life and others in danger – including his passenger and rescuers." .