Stavro99

I have an MTD Yard Master single stage snowblower. I opened up the side panel where the auger drive belt and pulleys are, and I saw that one of the pulleys is broken. The broken pulley is the pulled that is connected to the shaft that goes to the engine. The shaft is not stationary, it turns, so I have been unable to get the nut off so that I can put the new pulley on. Is there a way to lock that shaft down? Otherwise does anyone have any suggestions?

Thanks