Gasoline Venting

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Just as automobile technology is changing to match new environmental standards, so must our boats. Evolving awareness of open gasoline vents expelling raw hydrocarbons into the atmosphere has prompted re-engineering solutions. Some, such as the portable jerrycans with spring-loaded openings that we use for gasoline equipment at home, seem to spill as much as they used to vent. But some of the current engineering entering the world of boats mimics the vehicle rules and, thus, will start to seem familiar.

While new standards do not apply to existing gasoline boats with single direct vents, anyone buying a newer boat is going to find new features. The first familiar item is the gasoline fill cap, which clicks or gives some other indication that it is fully engaged and sealed, ensuring that any changes in tank pressure can’t vent hydrocarbons into the atmosphere.


Tank pressure increases with rising temperatures as volatile solvents are released; pressure decreases with high demand from the engine as fuel is consumed and air fills the empty space. One way around this is to use a bladder tank, but nearly all recreational tanks are a fixed size. One of the best methods to stabilize tank pressure is a second venting system with a carbon canister that blocks the escape of vapor when the tank is above atmospheric pressure.

The canister acts as a catalyst, consuming volatile solvents rather than allowing them to release. It will not work if it is flooded with gasoline, so there are safeguards (just as with our vehicles) to ensure proper fill levels. The canister also cannot get wet or flood with water, which means more safeguards.

None of these eco-friendly evolutions will affect your boat’s operation, but it will be a little “greener” as vapors stay in the tank.

This article originally appeared in the April 2018 issue.