hydrofoil install

[fishinforfun61]

hello, I have an 83 evinrude 25hp and want to install a hydrofoil on it but it has a small rectangular piece on the fin that is screwed on first off can anyone tell me what this is and can it be removed in order to install the foil? any input will be greatly appreciated, thank you.

[boats.net]

That piece needs to stay installed, it works with your cooling system.