Torque Tab ??
 

Scroll thru the pics and look at the Skeg that has rivets IMO a torque tab was installed starboard side of the outdrive skeg. I know a lot of fast outboard engines installed torque tabs more so in the past as well. But I really do not recall a sterndrive installing rivet on torque tabs. I understand what they do but kind of wondering about this install on the 29

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What does it do?

It counteracts torque steer, not sure why is would be needed with an ITS box/hydraulic steering.

Let the boat tell you what it needs.

Your outdrive is turned slightly to counteract the torque caused by the rotation of the propeller.
The torque tab counters that prop torque and thus the drive goes straight through the water instead of slightly crabbed to the side.
The drive going straight instead of crabbed means more speed.