This looks like it goes some place...?

[Rattletrap]

Found this sitting on top of the block rubbing on the belt. Looks like it goes on either side of the carb; maybe at the air intake(?) iDK

Started dinking with carb last fall and got busy. I just cleaned out the fuel line and carb and found this while I was testing out the engine.

 

[Rattletrap]

looks like part #853526, Insulator.

 

[mechanicman]

It goes between the carb and the intake. Should be a gasket on both sides

 

[Rattletrap]

Thanks. It looks like I’m short a gasket, which is no longer available. Is there a common replacement gasket available?

 

[mechanicman]

If you can't find a gasket. You can make one using a good quality gasket paper. One that is fuel resistant.
The gasket actually looks like a newer mercury 15hp 4 stroke gasket. Possibly 2013 and up