Mr Johnston joined Godfrey Cohen as a partner in 1936 when the vacuum chain had just one store in Melbourne.
At its peak,Godfreys was snapped up by private equity investors CCMP Capital Asia and Pacific Equity Partners (PEP) for about $300 million in 2006.
In recent years,the chain's fortunes have been failing,but Mr Johnston was seeking to revive the business after buying it back.
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He was active until the end,opening a new Godfreys store in Adelaide in October.
Godfreys chief executive John Hardy said it was a sad day for the company,which has more than 220 stores across Australia and New Zealand and about 460 employees.
Mr Hardy said Mr Johnston was"the driving force"behind Godfreys'growth into a national retail chain.