Whangarei Coastguard volunteer president Brian Whimp said they were notified of an urgent callout after the vessel's engine failed about 8pm on Saturday.
The coastguard vessel Circa Rescue was launched from Marsden Cove in rough conditions.
They had been given the boat's location as "in the vicinity of the Old Woman", near Ocean Beach.
They took a circular route at about a fifth of their boat's maximum speed due to the rough sea conditions.
It took them one hour and 15 minutes to reach the stricken launch, which had drifted a further four nautical miles past the Old Woman. Mr Whimp said the boat had been difficult to spot and precarious seas meant a rescue plan was devised quickly.
"We only had a matter of seconds to make the decision ... there was the possibility of them crashing into us."
The couple were rescued but it was too unsafe to tow their boat.
"I think the lady, she was pretty keen to get off ...
"The man was pretty unimpressed when we told him we couldn't tow his boat," Mr Whimp said.
Swells picked up to 3m on the return journey to Marsden Cove.
Despite the disappointment of losing their boat, the pair were "very grateful and happy to be on shore", Mr Whimp said.
Mr Whimp urged boaties to carry two forms of communication, ideally a cellphone and a VHF radio, and to check marine weather forecasts carefully.
Northland Regional Council deputy harbourmaster Chidambaram Surendran said they had issued a maritime warning to all vessels alerting them of the drifting boat.
Larger vessels further out to sea would not be at risk of damage if they hit the launch, but it would be more dangerous closer to shore for smaller craft.
Mr Surendran suspected the boat may have continued floating out to sea, but said it was hard to predict where it would have ended up.
He would expect boaties to notify the harbour master if the boat surfaced nearer the coast.
