Fuel System Question

[gsbarry]

Anyone have an idea of what this fuel system part circled in the pic below (black cylinder) is/does? It appears to be sitting in line on the fuel vent hose mounted on top of the tank. This is on a 2015 Bayliner 175.

 

[Bt Doctur]

says epa compliant so I think its hooked to the vent line, maybe a whistle device to indicate a nearly full gas tank

 

[04fxdwgi25]

or a vapor charcoal canister.

 

[Scott Danforth]

vapor canister required on newer boats