What is that part?

[thadula]

Does anybody know what that part is? It's from Searay 180 Bowrider 1998, Mercruiser MCM 3.0 litre 181 cid / serial: 0L069875, transom serial: 0L267053, sterndrive Alpha One Gen II / serial: 0L184205. There were 2 plate like that: one fell from the drive lower unit when replacing an impeller and the other one appears to be stuck in the exhaust.

Picture of it here: https://drive.google.com/file/d/1Rsg...ew?usp=sharing