I have thrown a prop during starting that was not primed at all. It is a .91 4 stroke and I never prime it since I use a starter. And it has the prop nut and the lock nut from Tru Turn for the aluminum spinner. Yet it has come loose at least 3 times during starting last season. So I thought the lock nut question is very valid. I'd like to hear more opinions. So long as it doesnt affect engine balance, why not? Just as an FYI, Iam a 30 year A&P so Iam pretty sure of my installation techniques. Yet obviously something is not right.