I want to change change the prop on my buddies 50 hp Merc. I'm use to a cotter pin, I looked at it quick and didnt notice any cotter pin, it has the 2 two tab washers(tabs look bent up) and a locking nut. How do I do this, should I knock down the tabs so I can turn the nut? Will the prop come off easily? Do I have to mark anything?