2-Stroke 2001 1200gpr cylinder question

[rudysnx]

I have a 2001 1200gpr. The previous owner purchased a full engine from SBT in 2008. The cylinder closest to the stern was damaged from what I believe is water getting into the cylinder so I ordered a cylinder exchange kit from SBT that arrived a couple days ago, to replace all cylinders, pistons, etc. When I started removing the old cylinders I noticed that the middle and stern (PT?) cylinders had a small part held in with a screw into the cylinder (see pic new cylinder on the right), however the magneto cylinder did not have this "part" (see pic). All three of the new SBT cylinders had the "part" with the screw in them. So, does anyone know what the "part" circled in red does, why would one of the old cylinders not have it, and what does this "part" do? TIA I appreciate any advice and input.

[rdavis]

It had it at one time, they are anodes like all marine engines. If you aren't in a lot of salt water, I don't think it will hurt anything.

[WFO]

sacrificial anode. id definitely run one and I have some used ones if you need

also please dont use copper coat on a Yamaha engine!