Sorry, I am not familiar with the mechanism of the irwin. In my sabre there is a stainless steel tube with a cap bolt in the bilge area. The bolt gets removed to expose the tube, you can then insert a pipe ( supplied) to help push a stuck centerboard down. I remove the bolt in the winter, which allows any water that ingresses in to the bilge thru the top of the mast to overflow and escape through the centerboard slot.
Perhaps, Irwin made some provision for this too? Hopefully some Irwin owners will weigh in.