Fullers spokeswoman Delyth Morgan-Coughlan said that although the two breakdowns were unfortunate, both vessels were back in service in time for Friday morning sailings, and the latest increases from an annual fare review were unavoidable.
She said the breakdowns came while the company's other large vessel, the Quickcat, was out of service on a maintenance survey.
That meant a greater reliance than usual on smaller vessels, although the Quickcat would be back on the run at the end of this month.
Ms Morgan-Coughlan said the fare rises averaged 1.87 per cent and Fullers was delaying increasing the price of monthly tickets until November 1. Their price would rise by 1.4 per cent, from $350 to $355.
Although that will be less than the average rise, another ferry user said a 6.7 per cent increase on Friday for family return tickets - from $89 to $95 - would be hard on people visiting the island.