Prop nut, absolutely not. Your engine only came with one nut, there is no reason to run two. It's not like the TT 46 is prone to detonating and throwing the prop. Washer, that's up for debate. Personally, I say no since the Dubro nut has a large flat surface to contact the front of the prop. Others might say yes as you do not want the nut to turn against the prop face while torquing the nut. Again, personally, I run these, and other large after market nuts, without the washer and have never seen, or heard, of a problem caused by this practice.

John