Power supplies to Magnetic Island will be interrupted from approximately 9am till 1pm tomorrow as Ergon Energy crews conduct emergency repairs to fix the problems which have caused two large black-outs in the last week.

An Ergon Energy spokesman said crews found malfunctioning insulators on steel towers carrying 11,000 volt powerlines on hills between Picnic and Cockle Bays this afternoon.

To undertake repairs, power to Picnic Bay and Nelly Bay will be interrupted at approximately 9am and should be restored by 1pm he said.

Power was interrupted to about 750 customers during last Wednesday night's rain and strong winds and then again yesterday afternoon.

"On each occasion powerlines were patrolled but today's closer inspection in hard to access hill areas revealed malfunctioning insulators.

"Ergon Energy apologises for the interruption and will work quickly to undertake repairs and restore power as soon as possible," he said.