WHAT IS A CARBON CANISTER AND WHAT CAUSES IT TO CLOG?

A carbon canister is just that, a canister filled with carbon granules. The vapors from the tank run across the carbon’s large surface area when it leaves the tank and the carbon collects the hydrocarbons from the fumes. If the carbon gets wet from water from the outside of the boat through the hose and the p-trap vent or fuel from the tank through the hose, it can cause the carbon to break down and clog the canister. During fueling, the air that needs to escape through the canister cannot and the pressure builds in the tank and shuts off the nozzle.