Setting an Outlook 2013 task recurrence hourly is not possible “out of the box”. If you want to set a task to reoccur hourly in Outlook the workaround would be to create separate daily tasks for each hour that you need to be reminded.
If you want to be reminded of a task at 8am, 9am and 10am each day you would need to set up three separate daily tasks:
Task 1 – Recurrence Daily at 8am
Task 2 – Recurrence Daily at 9am
Task 3 – Recurrence Daily at 10am