(2) Whenever the port issues general obligation bonds for purposes other than refunding general obligation bonds previously issued and for purposes other than providing funds to meet the obligations of the City of Portland assumed pursuant to ORS 778.020 in an aggregate amount equal to five percent of the present real market value of all the taxable property within the territorial limits of the port, no additional general obligation bonds shall be issued for purposes other than refunding general obligation bonds theretofore issued without the approval of the electors of the port expressed at an election within the port at which such question is submitted. [Amended by 1971 c.399 §1; 1997 c.461 §2]