You’re out boating on a beautiful sunny day and, all of a sudden, you hear the motors giving out. You quickly realize that the fuel is running low. So you head back to the marina for a quick refill.
After refueling, you yank out the hose, and in turn, the frail chain holding the dangling cap breaks, and it falls in the water.
Now, it’s at the bottom of the ocean, and you’re out of a protective seal to keep your gasoline secure in the fuel tank. The solution to this seems pretty simple, right? Just buy a new gas cap.
Well, I’ve got bad news for you. Unlike gas caps found in cars, which are all the same fit, boat gas caps are an overly complicated component. They come with so many different sizes and styles that finding the right one on your own could prove to be a very cumbersome task.
A Little Refresher On Gas Caps
Just like cars, boats with motors also require fuel to operate. Likewise, boats also have fuel tanks situated under their decks.
A big pipe is connected to the fuel tank that comes up to the deck’s surface, which is called the ‘gunwale’. On the gunwale, you have your ‘deck fill’.
This is essentially your inlet to the fuel tank. You refill your boat by inserting the fuel pipe in here.
‘Fuel fill’ and ‘gas fill’ are two other names for it.
Every deck fill has a cap on it to protect the fuel from spilling out and prevent any gasoline vapors from escaping the tank. This also ensures that you’re not wasting a single drop of fuel and utilizing all of it.
Every ‘gas cap’ is built differently from the other one. Some are made out of metal, while some get the plastic treatment.
Sizes also vastly differ as both the cap’s diameter and the deck fill’s opening are different on different kinds of boats.
On top of that, the threading which secures the cap in place is also dissimilar in almost every case.
Threading of the deck fill itself is also crucial in finding the right replacement gas cap.
The only thing that remains the same throughout most gas caps is the chain that keeps the cap connected to the deck fill itself. But even that has seen a replacement these days, with hinges present in more modern and bigger boats.
Why Are Boat Gas Caps Different?
Different manufacturers make vessels that all have their unique ways of tackling the engineering that goes into making a boat.
For example, boat makers take different approaches to how the actual fuel tank is built on one. Some have the fuel tank permanently attached to the craft, while some offer a portable option that you can take out of the boat conveniently.
Similarly, the diameter of the deck fill is distinct from one another. This greatly depends on the size of the boat. The neck of the deck fill is smaller and usually matches the gas cap diameter perfectly.
The gas cap on the deck fill is also very different in size. The bigger the size, the more expensive.
You can also get the cap in different finishes like matte and gloss. Most metal gas caps come with a mirror finish.
There are different locking mechanisms too. In contrast, others don’t have any and just screw back safely into place.
Many high-end boats use expensive metal gas caps that have ‘o-rings’ inside, which help secure the cap more tightly. Even these o-rings can be of contrasting qualities. But thankfully, these can be found pretty easily. Also, these can adapt to fit many different cap sizes since they’re made out of rubber.
The Choice Made For You
To save costs, manufacturers cut corners, which can lead to them using a cheaper plastic gas cap, but if that’s the case, then it’s likely going to be an OEM one, which means that it’s not custom-made and already widely available in the market.
The more expensive the boat, for example, a speed boat, the more chances there are of the maker choosing to opt for an in-house design that forces the deck fill and the gas cap to be very specific. This can make it difficult for you to find the exact replacement later on, and calling your dealer might be the only solution here.
The 2011 EPA Mandate
Back in 2011, the United States Environmental Protection Agency decreed that moving forward, fuel systems on all new boats need to be sealed completely shut and disconnected from the outside.
The EPA did this to protect the environment from harmful and dangerous fuel vapors coming from the fuel tank. A sealed fuel system would allow for the air quality around the boat to remain as unaffected as possible.
With this change, manufacturers had to shift from a ‘vented system,’ where the cap would have physical holes in it for ventilation, to now, a sealed system that did not have any ventilation holes at all.
You need to be wary of what type of fuel system is present in your boat. Consult your dealer or the boat manufacturer if you can. A boat professional would also be able to tell you about your fuel system.
It is vital to have this information because when you buy a replacement cap, it can prove to be very dangerous if you chose the wrong one.
Installing a ventilated cap on a sealed system would destroy the sealed fuel system’s whole purpose, polluting the air by allowing the fuel vapors to enter the atmosphere.
Likewise, installing a sealed cap on a ventilated system would build up immense air pressure inside the fuel tank, and that is incredibly dangerous.
Are Boat Gas Caps The Same?
To answer the question, no. Boat gas caps are not universal.
They are heavily diversified, and finding a perfect replacement can seem like a bit of a challenge. On the other hand, in eco-friendly boats like small sailboats, that’s not an issue at all as they run on wind.
Your best bet here would be to ask around in the boating community. Talking to an expert friend, contacting your dealer, or to consult a professional who’s adroit in this regard.