May I ask what controller you use/intend to use?
We use Schneider PLC's and HMI's (controllers and touchscreens) and I have often thought of rigging up a returned one but there are so few electrical things on my '80s Fulmar it is not worth the effort!
Not sure how you would test the anodes, but if you are concerned there may be no anode left and are not going anywhere you could hang an additional one or two over the side on a wire electrically connected to the hull.
We used to do this on an aluminium race boat I worked on, permanent anodes...
I'm glad I am not the only one! The second hand book sellers must have wondered what was going on. Again, did not find it matched my humour. Michael Greene's effort I read time and again.
Could try disconnecting one of the terminals of the engine battery and see what happens?
Edit. Not with the engine running but see if it still kicks over.