Just a thought have you thought about taking the print out to the tauranga library in town. Although I dont live in Tauranga any more I know they had a great family section. Maybe by asking the staff there to have a look they may be able to figure out where otuhare is??? They may have old maps of the Tauranga area.
The Ringatu faith was and still is quite a stunch faith.
It was quite common for a child to take their fathers name as their surname. Hence the reason why Harihari surname is the same name as her fathers.
Another thing of interest is Harihari Rauwharangi mothers name. With Harihari mothers name being Te Whakaata Te Wherowher I do wonder if there is some connection to the Maori King Te Wherowhero??? (Not saying that there is) Could be another thing to explore.
I know you not tracing Mr Gage, but the name Hori Keeti translated is George Gage. Hence the reason for the library records saying Gage but the certificate saying Hori Keeti.
One other suggestions try the Maori Land Courts, give them a call to see if Harihari Rauwharangi, her father or mother had any land passed on to them. Quite often whakapapa was given when land was passed on. I found quite a bit of information there, death date of an maori ancestor which lead to a print out of a death certificate and another generation.
Ummmm that's about all I can think of at the moment, give the TGA library's family section in town a go you never know, they may point you in the direction for more information.
Cheers
