This link may also be of some help. http://www.marineengine.com/manuals/...l_numbers.html
He probably wants to sell you another prop as soon as that one falls off? The cotter pin holds the pin in place by holding the cap on the shaft.
If you take it to a decent prop shop they will rehub it.Or you can do what I did about ayear ago and do an emergency repair with epoxy resin.Still going
Part # 305294 prop nut.
Available right here at MN.com $9,99,
I will do those things and report back. Thanks