I have severe electrolysis damage below the water line on an 86 inline 6 115 Hp Mercury.

[Kvjimbo]

The Trim tab is magnesium and it has severe pitting.

If I use a wire brush on it will that improve it's effectiveness or do I need to replace it?

 

[racerone]

The trim tab is also a sacrificial anode and is doing what it is supposed to do.----It gets eaten away because of local water quality.----Replace it.----Do not paint it.----I have to chuckle when I see them painted.

 

[Kvjimbo]

The trim tab is also a sacrificial anode and is doing what it is supposed to do.----It gets eaten away because of local water quality.----Replace it.----Do not paint it.----I have to chuckle when I see them painted.

I've attached an image of the motor and trim tab. Why do I have severe damage with an intact trim tab?