What is this discolored plate on my stern drive unit?

[dburne]

Newbie question!
I noticed this plate on my stern drive was somewhat discolored during cleanup yesterday, what exactly is this, is this one of those sacrificial things I read about in the engine manual? I assume it is supposed to do this?

 

[Molson]

Yes, its an anode. You can also see one on your trim ram.

 

[dburne]

Thanks Jim, appreciate the info, I figured must have been something like that.