How do I clean this prop and rudder?

You might try some CLR or Lime-a-way mixed 1:1 with water. Try it on a small area first. Let it sit a minute, then rinse it off.   You may need to use a scrub brush. Just don't leave it on too long and be sure to rinse well. That should get the scale and copper sulfate off.
If that's too agressive, made try some plain white vinegar with some salt mixed in.
If not, maybe a wire brush?
If you get the crud off and you want to make it shiny, you can then use Emory cloth, soap and water and something like Tarn-x or Bra$$o.
I had the rudder off a couple of weeks ago and I polished it with emory cloth and then Bra$$o and a buffing wheel. I was bored. It made the machine marks really show up.

How about naval jelly? It works on other metal with stains. I never tried it on my prop.