Mohi's granddaughter Ronnie Tapsell-Walters, 37, said Mohi took a one or two-hour strolls every day around midday and believed he may have become "confused and disoriented".
She and other whanau remained hopeful of a good outcome.
"My grandfather suffers from outset dementia and a bipolar condition but otherwise he's physically fit and as part of his daily routine is a stroll around his neighbourhood.
Tapsell-Walters said the disappearance was out of character and she called the police after he did not return within two or three hours.
"We believe he is alive and will be found, it's just a matter of time.
"He might just need a ride home, to be honest."
She said her grandfather was humble, friendly, principled and dedicated to God.
People should not be afraid to talk to him if they found him.
"Just walk up and say 'hey John'. I wouldn't approach him and say 'are you John Mohi? You've been missing I've been looking for you', I would more put it in a friendly mannerism. If he replied to 'John' it must be him – maybe have a yarn to him."
Tapsell-Walters said lots of people had phoned in, and there had been unconfirmed sightings in Mount Maunganui, Rotorua and Whakatāne.
She said anyone who thought they saw him should take a photo to help police.
Tapsell-Walters said she and her whanau wanted to say a huge thank you for the "awesome" support from the community, including complete strangers.
Among the volunteers who searched for more than five hours yesterday was Pongakawa mother of three Kaye Rangi.
"I felt if it was my elderly grandmother missing I would hope other people from the community would rally to support my family," she said.
"While it very hot day, I really wanted to come along to support Mr Mohi's whanau," Rangi said.
Rangi said given the mass search efforts, it was "very deflating" he has not been found.
Another longtime Maketū resident and schoolmate of Mohi's, who asked not to be named, said he joined the search on Tuesday.
"John is a quietly-spoken, unassuming, friendly man and quite fit. This is out of character and John won't be hiding somewhere, as he has nothing to hide for.
"It's very concerning he hasn't been found yet. I've said a prayer for his safe return," he said.
Inspector Zane Smith said police and Land Search and Rescue were working closely with Mohi's family on the search.
Have you seen Johnny?
Name: Johnny Mohi, also known as Johnny Moses
Age: 77
Physical description: 183cm tall, slim build, short white hair, mole above his right eyebrow
Wearing: Last seen in dark grey tracksuit pants with the word "Starter" written in white on one leg and a navy blue checked polar shirt with white stripes on the chest and back area.
Movement: Walks with his head down in a stooped position
If you see someone fitting this description:
- Take a picture
- Contact Tauranga Police on 07 577 4300
- Approach him gently, see if he answers to John
