In 1986, Hawaii was a mediocre 7-5 team, which had coincidentally beat Wisconsin in the second game of the season (at Hawaii).
In 1998, Hawaii was the worst team in college football and had lost the previous week to Northwestern by the nearly identical score of 47-21.
Results from a decade and two decades ago aren't indicative of the offensive juggernaught they have now, which is why they've been able to beat mid-level Big Ten teams at home over the last few years. And their defense isn't nearly as bad this year. Again, I'm not saying they'd beat us (I seriously doubt they would), they'd give us more of a game than most here (who are lucky to have seen them play once or twice this year) would acknowledge.