Choosing a fuel bladder is not as hard as you would think. After all, they have to meet all the safety standards to even be on the market. That said, there are a few things you should pay attention to get desirable results.

For those who choose a fuel tank for their engine for the first time, it would be beneficial to get familiarized with the selection criteria.

Capacity

There’s no kill like overkill. The worst thing I can think of is buying something and then never using its key features. On the other hand, a boat is not a car, which means that it will not be possible to refuel it at sea, so you probably want more capacity rather than less. At the very least, you want to have an extra canister of gas on board.

When choosing a tank volume, you should focus on the fuel consumption of the motor. Also, make sure to account for how often you sail and for the average duration of your boat trips. Basically, you need to calculate how much fuel you would typically need, add from 30% to 100% just to be safe, and then make your choice.

Material

It is imperative that the material the fuel bladder is made of is durable. Since gasoline and machine oil both are, in fact, toxic and corrosive substances, poor-quality plastic can deteriorate over time. And that can have lots of consequences. It is okay if it is just a soiled boat, but fire may break out as well. It is best to buy fuel bladder made of durable plastic.

Some engines work on a mixture of kerosene and gas. In that case, you should have two fuel bladders, one for kerosene and one for gas. Kerosene tanks and bladders have to be exceptionally tight since kerosene is very fluid.

Then there is mechanical damage to consider. Resistance to it is significant for the strength of the tank and especially a fuel bladder. Fishing often requires some pretty active and dangerous moves. If you cast a bait, and the hook bites into a poor-quality fuel bladder, you can see how it’s going to go wrong. Even if you have a rigid fuel tank, the weight can make a crack on impact, and the gas fumes accumulated inside are going to escape unimpeded. That’s an explosion risk, no matter how small, and a palpable risk of drifting without fuel in the middle of an ocean. Not very pleasant.

All in all, the bladder material must be durable, chemically resistant, and elastic. 

Internal Pressure

A big concern for rigid tanks, less so for fuel bladders. Due to their stretchability, bladders handle internal pressure well, the capacity of the tank or fuel bladder also reduces the problem. Still, internal pressure has to be dealt with.

You have to be wary of the sun since it causes pressure to grow. When the bladder is heated, the fuel evaporates, and the pressure increases due to the gasoline vapor. If the fuel tank does not have a way to reduce the pressure safely, like a safety valve, it’s a fire hazard waiting to happen.

Monitoring the Amount of Fuel 

With fuel bladders, it’s easy. You can still err because of gas fumes inflating the bladder, so it’s good to have some other method to check it. With rigid tanks, it’s more of a problem.

But why is that such a big deal? It’s just a precaution. Each time you go fishing on a boat, you need to check how much gas is left in the tank. This will help you not to stall in the middle of the lake at the most crucial moment.

To help you with that, manufacturers usually paint markup on the walls of the tank, which should allow you to see the amount of liquid in the gas tank. But it’s only helpful when the material is translucent, and that’s usually not the case with fuel bladders.

But there is another way to monitor the fuel level. More sophisticated tanks and bladders come with fuel sensors used to determine the fuel level programmatically. The tank has to come with a screen to read the data, but it doesn’t have to be anything flashy, so that reduces the price drastically.

Finally, you can use the old-fashioned method: put a cord or a stick in the hole in the tank, pull it out, and check how much of it is soaked. But this method can contaminate the fuel, and it’s not suitable for horizontally oriented fuel tanks and most fuel bladders. It is better to choose a tank that has this problem solved by the manufacturer.

Sealing

When choosing a fuel bladder, you need to pay attention to such elements as the hose, fittings, and seals. If they leak when under pressure, all that high capacity is worth nothing.

Lid

The lid, while not the most crucial element, is still quite relevant. It has several functions: it prevents fuel leakage if the vessel rocks and pitches; it stops foreign bodies from getting into the fuel; and finally, it controls the internal pressure.

A good lid is not an ordinary cork. It’s bound to have an intricate design. Even if the lid has the appearance of a regular cork, it’s still going to have seals.

Replacing the stock lid is a pain, so I really advise not to lose it. It’s simpler than you would think it is. If the boat is idle for a long time, lids tend to disappear in the unknown direction magically. I never did manage to recover a single one. And all the replacement lids suck for some inexplicable reason and lose their sealing qualities reasonably quickly.

Don’t be me, please.

Tank Types

Today, you can find two fuel tank types: rigid tanks and fuel bladders. In both cases, the material is mostly plastic. Those plastics are very different, though, but hey both have to be durable and leak-proof.

For fuel bladders, leak-proof material is an essential feature. It’s easy to achieve with rigid tanks, but fuel bladders take shaped as they are filled with fuel, much like a balloon filled with water does. Accordingly, with each gallon consumed, the tank will “deflate.”

A rigid fuel tank is just that. It’s a fuel-tight container filled with fuel.

Advantages of Fuel Bladders

Fuel bladders will take the shape of the contour it comes in contact with and volume that allow space. Besides, it is always possible to check how much gas is left in the tank. Since the taken volume decreases as the gas is consumed, the accumulation of fumes is not really a thing. From a security point of view, that makes fuel bladders optimal.

Fuel bladders also have more capacity than traditional fuel tanks or comparable size.

Disadvantages of Fuel Bladders

They are expensive. Really, really expensive. Unless you want to mount one on a military or rescue boat, you should have an excellent reason to buy a fuel bladder rather than a traditional fuel tank.

Useful Extras

As far as extras go, manufacturers have come up with several nifty details.

Consider a handle, for instance. It makes carrying the tank or fuel bladder extremely convenient for the operator to carry. Digital sensors allow you to monitor fuel consumption and tank pressure. Extra filters clean the fuel mixture before it even gets to the engine.

However, all that is going to cost you money. The extra features are not the only thing to affect the price. Aside from them, the price depends on the material of the fuel bladder, its capacity, and the brand. Fuel bladders are also much more expensive than traditional fuel tanks.

An ordinary low capacity (2-3 gallons) horizontal tank with a simple lid of can cost up to $50. If the volume is increased to 25 gallons, up to $200.

Portable fuel tanks with a capacity between 2 and 8 gallons will cost you from 30 to 60 dollars. Also, if you want to have an automatic sensor or an extra filter, then you will have to pay for them, as well.

A fuel bladder is going to be twice as expensive as a rigid fuel tank. A 25-gallon fuel bladder will cost you almost $600.

And then there is the matter of brand recognition. A no-name product will cost you cheaper, and if it works fine, it’s okay. However, there is a problem with accountability if we’re talking about foreign brands, while domestic brands may have issues with things that big names have long left behind.