J40ELCDE
G7100857

I recently acquired a 1986 Johnson 40hp outboard. It was used in lake water and now I plan to use it in the sea. So I want to change the sacrificial anodes to aluminium.
I am trying to identify where all the anodes are placed. The service manual is not very helpful with this. So I looked up the "exploded view" of the gearcase here:

https://www.boats.net/catalog/johnso...elcde/gearcase

It seems there are 2 anodes (parts 77 and 80). 77 is easy to change but I am wondering about 80. If I have interpreted the picture correctly it is in the gearcase and I would have to remove the lower unit. I've looked up some youtube videos of the same/similar engines, but none of them seem to have this anode.

Before I remove the lower unit, I was just wondering whether anybody had any experience with this that they can share. Is anode 80 necessary? Should it be there in practice? Or will anode 77 take care of the job by itself?

Also should the trim tab on this motor be sacrificial?

Thanks