I think you need to use Standard Operations for this. A standard operation can be referenced in both part routings and routing templates, and then if you update the standard operation the change can be pushed to all places where used.

Some of the part routings are not related to a template.     I need to replace an operation with a newly created one so it is not an update.    I see that you can update a template and push out changes to all the related part routings but I am wondering if there is any automated way to update part routings that are not associated to a template.

Have you done this?