You're kidding, right?
You must not ever use copper bottom paint on an aluminum LU. You created a battery, with the aluminum failing first. Now you will need to sandblast the LU clean to fresh metal, possibly etch it using a 2-stage chromic acid etch (such as West System sells), and give it two good coats of epoxy. That will be a chore, as you don't want to sandblast the prop shaft, etc., but you do need to blast the prop, the prop shaft housing, and the LU casting itself, plus any of the driveshaft housing that is immersed all the time.
You can then use a long-life specialty paint such as Coppercoat (which is in fact copper, but will be isolated from the aluminum by the epoxy), or Pettit Ultima, Pettit Hydrocoat Eco, or Interlux Pacifica or the old standby aerosols of Pettit PropCoat, Pettit Alumispray or Interlux TriLux 33.
The water inlet strainers are plastic, so the paint may or may not stick to them. Scrape the zebra mussels off the strainers periodically with a piece of wood.