Police say a forensic examination of a boat found with no-one aboard off the Taranaki coast may offer clues about what happened to its owner.
It has been 10 days since William Kerry Blair, 55, left the Marlborough Sounds in his nine-metre aluminium launch Erie.
The HMNZS Wellington reached the launch more than 200 kilometres off the Taranaki coast in heavy seas late on Monday night, after it was sighted at the weekend.
Police officers on board the Navy vessel managed to board the Erie despite a 10-metre swell.
Mr Blair, known as Kerry, left the Sounds on the Erie on 8 March.
The HMNZS Wellington is trying to tow the Erie to New Plymouth but police believe sea conditions will prevent it arriving on Tuesday.
Once the Erie is in port a detailed examination will be made to try to establish what happened to Mr Blair.