Replying to Yo chem/boating dogs!

the chunk of metal on the back of boat motors is zinc. (acts as a cathodic protector to prevent rusting)

few questions:

1. Is there no aluminuim on the outside of a boat engine, because aluminum is a stronger reducing agent, and would therefor rust first, would it not?

2. Why (or are there?) no cathodic protectors on the hull of the boats, and if the boat hull was all aluminum, would the cathodic protector have to be something of a greater reduction value, such as magnesium?