Tauranga man Peter Blair remains hopeful his missing brother can be found as the search for the 55-year-old seaman is stepped up.

A Navy vessel and RNZAF Hercules are today en-route from Wellington to help search the area around where William Kerry Blair's 9-metre launch Erie was last spotted on Friday.

William Kerry Blair (pictured) has not been heard from since heading out on his 9m launch on March 8.

Kerry has been missing since heading out on his boat from the Marlborough Sounds on March 8.

On Friday, March 14 the RNZAF Orion located the launch Erie about 200 kilometres off the coast of Port Taranaki, but high seas made an attempt to board the boat, or bring it to shore, impossible. A large oil industry ship equipped to operate in heavy seas was also dispatched to try to reach the boat.

'It's extremely frustrating and a huge waiting game,” says Peter, speaking from Picton today.

'It was not good for those young ones [Kerry's children] they are beside themselves I can't describe it. It's just awful for them.”

A naval vessel is left Wellington last night and is expected to reach the location at about midnight after being pushed back from 3pm today. A RNZAF Hercules will also be deployed if needed.

Peter says the family also have a 20m vessel and crew ready to go out, should the Navy decide not to make an attempt.

Peter says when the boat was located by the Orion they were not able to tell conclusively whether Kerry was still on board the boat, but it was found upright.

'It was sound and appeared by all accounts water tight and safe, but still no signs of life.”

Kerry is an experienced seaman and setting out without telling anyone of his intentions is out of character, says Peter.

Since appealing for donations to help cover the extensive search costs, including the Orion and Hercules flights on March 12, Kerry's children have raised more than $15,400 through givealttle.co.nz.

'The family are extremely overawed with the support that we have got throughout New Zealand, it's phenomenal.”