Booting iMac8,1 off USB

I am having some trouble booting my iMac off ANY USB with any OS. My DVD has been replaced with SSD from which I'm running Mac OS. My original HD I use for data.

Is this a problem with old machines? Or am I just doing something wrong. I just cannot boot my BOOTCAMP created USB. I've tried many bootable USB creators with different options, so I don't think that's the issue.

The symptom is always the same. I press opt key, I see my USB as "EFI". When I select and hit ENTER, it hangs. Mouse freezed. Nothing. No error or anything.

If someone can at least let me know if I'm wasting my time.