The Coastguard says the vessel was "at the limits of its operating capacity" while the head of the Westpac rescue chopper called the situation, "unbelievable".
The tragedy marred an open day at the rescue chopper's base when children witnessed the dead men's bodies being carried to shore.
Water Safety New Zealand chief executive Matt Claridge told the Herald there had been too many preventable deaths. "It's a really hard lesson to learn for paying not enough attention to safety ... what really needs to happen [is that] the blokes going out on the water really need to look after each other - and think about the family they are leaving at home."
People taking boats out needed to do a boating education course. "There's a good old saying 'the more you know, the better your boating', and it's quite true. The more you do know then the more experienced your decision-making will be."
Mr Claridge said Water Safety New Zealand was putting resources into reaching out to the Pacific Island community. "They do go out on the water and do go to fish, and the water in New Zealand is just too different to the Pacific Islands and it's usually the men - they're going out and probably leaving families to fend for themselves without a father."
According to Water Safety, 8 per cent of total drownings between 2007 and 2011 were Pacific people, with 87 per cent of the victims being males. About three-quarters of the deaths occurred during a recreational activity.
Coastguard northern region chief executive David Tommas said the Manakia was probably overloaded and too small for the conditions.
"It was blowing at 20 to 30 knots out there and the sea was running at 1.5m to 2m. We believe the vessel was 4.9m long which, for seven people, is probably at the limits of its operating capacity - particularly in this weather."
Sergeant John Saunders said when the ill man moved from the bow to the back of the boat it "had the effect of lowering the stern very close to the water".
"They took on water over the back of the boat, and the effect of all the water and the seven occupants caused the boat to roll."
A nearby vessel raised the alarm and emergency services rushed to rescue the men, who had become separated in the water. Three were picked up by a nearby boat and two others by a Coastguard vessel.
The last two men found had been in the water for about 45 minutes and were "unconscious and unresponsive".
The men, all friends and family between the ages of 25 and 50, were from Kiribati, Tonga and Rarotonga.
Westpac rescue helicopter chief executive Bob Parkinson said: "It's just another example of overcrowded small boats in challenging conditions where people are inadequately prepared.
"It's just unbelievable. It's really quite a challenge how to get this safety message across."
The deaths bring the drowning toll from powered craft this year to 22, and the total number of drownings for the year to 83.
-additional reporting APNZ
