How to remove the fan on an AEG 90w motor?

I have a Worcester Danesmoor 20/25 boiler syetem. When running it howls loudly, I am sure that it is the fan motor. I have removed the little AEG 90W 0,85A motor but how can I remove the fan. The fan appears to be pressed onto the shaft. Will I need to purchase a new motor with a fan fitted?

Please help.