He said the average mortgage he brokered was about $280,000 over 30 years, which at a rate of 5.75 per cent had weekly payments of $377 per week.
With an increase to 6 per cent interest after an OCR rise, this would be $387 per week.
With similar rises predicted each quarter, this would be an extra $80 per week for many people, he said.
Rothbury Insurance Brokers Tauranga mortgage adviser Keith Ardern said the initial increase would not worry many people as rises had been talked about for months.
Mr Ardern said mortgages arranged by his firm recently allowed for such an increase.
"Generally I'm advising a fixed rate for 18 months to two years, depending on individual circumstances ... The floating rate may be affected with short-term fixed rates but it seems banks have already anticipated a rise in the OCR and have adjusted their long-term fixed and mortgage rates."
Mortgage broker Chris Rapson, of Rapson Loans and Finance, hoped the Reserve Bank would not put up the OCR today as it would be bad for the Bay of Plenty economy.
"It gives the banks license to increase their rates and that all ends up in Melbourne or Sydney. It takes money out of Tauranga."
Mr Rapson said the people "rattling sabres" about the increase were those whom he believed benefited from creating volatility.
"It makes people worried therefore they fix their rates when really they don't need to. I think it's verging on scaremongering."
Mark Lister, head of private research at Craigs Investment Partners Tauranga, said he did not think OCR changes would make a huge difference to the average Tauranga homeowner.
He said fixed mortgage rates had already moved, to some degree, in the past six months to reflect the changes.