An evaporative emissions control canister for adsorbing fuel vapors from a fuel tank on a marine vessel. The canister comprises a polymeric extruded housing that may be formed to any desired length or cut from extruded stock. Identical end caps having tubing connectors are bonded to opposite ends of the housing, defining an inlet and an outlet. Marine-grade pelletized activated carbon is disposed within the housing between porous slidable plates that are spring loaded against the end caps to pack the carbon tightly against the housing walls. Mounting brackets at each end are rotatably attached to the end caps so that opposite ends of the assembly may be attached to different surfaces of the vessel's hull, thus relieving stress which might be introduced into the assembly. Preferably, the assembly is wrapped in a fire retardant material.