Easy Steps On How To Build A Boat Fuel Tank Out Of Scratch!

You bought a nice shining boat but as you start using it, you notice that the builders of the boat have violated some of the most important standards of boat tank design and installation.

It will not only affect the lifespan of your boat but will also create a hassle for you many a time. In this case, what you need is to build your boat fuel tank. Yes, although it is quite easier to just buy one premade that follows the standards, your budget may not comply with it. Hence, your last resort is your DIY boat fuel tank.

Now, the question that is supposedly on your mind bringing you here is ‘how to build a boat fuel tank?‘ Although the whole thing might sound complicated to you and make you worry about the end product, just following the basic steps correctly will end your worries with a shining new boat fuel tank in no time!

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What Material Should You Pick for Marine Fuel Tank Fabrication?

The right material depends on a few unwritten factors, such as the size of the boat, how big your tank will be, where they are mounted and how they are mounted. Now, in the case of selecting a material for marine fuel tank fabrication, there’s always a competition between the aluminium fuel tank and stainless steel fuel tank. 

Considering all the aspects, the aluminium tank fits our requirements more than any other material. Why? Let’s see the advantages-

  • Aluminum will not rust
  • Lightweight
  • Cost-effective, a must for builders with a strict budget.
  • Aluminum is stronger and sturdier than plastic fuel tank
  • There are baffles in the aluminium tanks adding to the stability.
  • Resistant to the heat and sunlight effects than other materials.

Even though now you know you want to make your fuel tank out of aluminium, there’s still more to know about the different aluminium types and what you can use for the tank fabrication. 

You can make your tank out of weldable aluminium that is.040″ or.050″ thick. 2024 T3 grade aluminium alloy sheet can be used if the tank is riveted and no welding is necessary.

However, 2024 T3, in addition to not being weldable, is difficult to shape unless it is in its annealed state. Otherwise, utilize an aluminium sheet from the 1100, 3003, 5052, or 6061 series, which are routinely available as weldable aluminium alloys.

I would not recommend the use of the soft commercial 1100 aluminium because of its lack of strength. Heat treating 6061 aluminium after welding is possible, however, this is home builders are rarely eager to do it.

Considering the essential aspects, the best fuel tank material is 5052 or 3003, either 1/4 or 1/2 hard aluminium that can help your tank retain a good shape and durability period.

No matter, where the problem with your old tank is it doesn’t fit properly, comply with the standards, or if simply you want added fuel storage capacity, build a new boat fuel tank with the required adjustments, you can fulfill your needs like a pro.

How to Build a Marine Fuel Tank: The Process

Now that we know which material to use for the boat fuel tank setup, let’s dive in straight into the process on how to make an aluminium fuel tank!

Marine fuel tank installation requirements

When aiming to build a marine fuel tank, you need to keep in hand the following things-

  • Measuring tape
  • Paper and pen to write down measurements
  • Cardboard
  • Tape
  • Aluminum plate, preferably H4 3003.125/ stainless steel plate
  • A 40-50T carbide blade skill saw
  • 90-degree clamps
  • Welding tool
  • Prefabricated pickup/ vent

With the tools and materials at hand, it’s time for the homebuilder to dedicate his time to making the perfect aluminium boat fuel tank.

1st step: Fuel tank design

We’ll begin by taking numerous measurements of the area where your gasoline tank will be installed. This will take a long time, so have a piece of paper nearby to sketch up the design and record all of the measurements.

Keep in mind that any fuel pick-ups, fuel filler, fuel level sensor, vents, mounting strap, and of course fuel lines will need dedicated space in the tank.

Also, make sure the tank isn’t in a position where the exhaust would cook it, or if that is the case, make sure you plan to build some heat insulation around it.

2nd step: Making your DIY fuel tank model

Now that you’ve sketched out your idea, it’s time to turn it into a working prototype. Why is the prototype necessary? No matter whether you are a rookie or a professional, a prototype can save you from losing bucks and getting the right design costing just a few hours extra. 

The last thing you want is to spend hours crafting a fuel tank out of costly materials only to discover it doesn’t fit or that you overlooked something in the design.

Hence, the simplest method is to use cardboard. When it comes to any type of fabrication, cardboard is your best friend. You need to make a cardboard model of the tank using all of the measurements from your plans.

Make sure the cardboard replicates the real sheet metal sections you’ll be cutting out to build your tank. Make sure the cardboard fits into your designed fuel tank by taping it together.

3rd step: Material selection and tank cut out

With your cardboard model at hand, an aluminium plate, and a 40-50 teth carbide blade saw, you are ready to cut out the measured cardboard pieces into the actual plate. 

You may be thinking of it as rocket science, but believe me, it’s not. It’s pretty simple with a nice skill saw as listed. We would usually prefer the 5052 aluminium plate or H4 3003 as I mentioned earlier.

However, if you are building a steel fuel tank out of mild steel or stainless steel, let’s look at the pros and cons of these materials.

Mild steel:

It’s alright to construct a mild steel fuel tank, but keep in mind that mild steel is corrosive, so you’ll need to take extra precautions.

You’ll need to coat not only the inside but also the outside of the custom fuel tank for boat. It’s a time-consuming operation, and if the coating isn’t done correctly or you don’t get enough coverage, it could be disastrous.

Many people have also reported that the coating does not keep up well after seasons of use. As a result, mild steel is the material we frequently avoid.

Stainless steel:

Stainless steel is an excellent choice for a gas tank. It has strong corrosion resistance and is relatively easy to weld.

While it is more expensive than mild steel, it is likely to cost approximately the same once you include in the pricey coatings that must also be bought in case you use mild steel.

If you can’t weld aluminium, this is your go-to material. But how to build a stainless steel fuel tank? Don’t worry it is the same procedure.

While I have earlier pointed out the advantages of aluminium, it has disadvantages too. Welding aluminium fuel tank is difficult but once you get it right, it will save you from costing extra bucks.

4th step: Building the marine fuel tank baffle

After you’ve picked your material and have it all cut out, you’ll need to figure out how you’re going to cope with tank slosh. Tank slosh occurs when the petrol in the gas tank moves about as you turn a corner or accelerate.

When fuel flows about, it has the potential to deplete the fuel supply at the fuel pump if the car is running out of gas. This may be fatal, not only in terms of burning out a gasoline pump by driving it dry but also in terms of generating a lean air-fuel condition in the engine and causing it to grenade. So, to resist the tank slosh, here are a few options to try out.

Building a fuel sump:

A sump is a built-in compartment in the tank that surrounds the fuel pump pickup. To keep the pickup immersed in fuel, this space has walls constructed up around it.

It usually has small openings in the bottom of the walls to let little amounts of fuel in and out, but it won’t allow large changes in the fuel system at any time. In addition, the return fuel line is emptied into this space to provide fuel.

If one wants to tackle fuel shortages, gasoline sumps are necessary. The simplest approach to construct a sump is to construct a circular foundation with a diameter of 4″-5″ and a height of 14 times the height of your gasoline tank.

Making a fuel cell foam:

Yes, a fuel cell foam is precisely what it says on the tin. It’s a foam that’s resistant to fuel. The sloshing motion of the fuel is slowed by packing the fuel tank with foam.

By slowing the sloshing action, you expect to have enough time to get through the corner or finish the acceleration, allowing the fuel to return to the fuel pump pickup. 

While the foam approach is the simplest, it won’t work in extreme sloshing circumstances or tanks with enormous dimensions that enable the fuel to flow about freely inside.

Using trap doors/ tank dividers:

If you examine any track/race vehicle fuel cell or tank, you’ll notice that it’s separated into parts or little cells with trap doors or small holes between them. Essentially, this technology divides any large fuel tank into multiple smaller ones.

Tank slosh isn’t an issue in small gasoline tanks because there’s nowhere for the fuel to go. As a result, the pickup for the gasoline pump is always immersed.

Small holes or hinged doors are bored into the bottoms of these wall dividers to let fuel slowly flow between the cells, but any sudden acceleration will prevent much fuel from moving at once. You can also purchase baffle doors, drill in some holes, if building a trap door is of much work.

5th step: Gas tank welding and fixing

It’s time to get to work on the welding. Long welding with long spans of heat is common in fuel tanks, causing a lot of bending and movement of the metal. To be successful, make sure your tank is clamped in as many locations as feasible before you begin.

Then come to terms with the tack weld. When you go back to conduct the final passes, tack welding will hopefully maintain things straight and from moving. Furthermore, make sure you’re welding in different regions of the tank.

Don’t just slap a side of the gas tank on and call it a day. Set it up, affix it to the wall, and then go on. Some 90-degree clamps are useful here.

6th step: Adding the final pieces

Laying out the last elements that will flow fuel in and out of the tank is the final phase in any fuel tank building.

You can use a prefabricated pickup/ vent from Amazon for the tank  The tank in this case utilizes a prefabricated pickup/return/vent package that we bought on Amazon.

What you need to add here are only a filler neck and a fuel level sensor.  If you won’t be filling the tank with gas from the manufacturer, make sure there’s enough room for a huge fuel door that can be opened to fill the tank.

To mitigate the curiosity, let me tell you this tank can weigh up to 23-25 lbs, that can hold 12-14 gallons of oil.

7th step: Check for leaks

Pressure testing is the way to go if you don’t want any leaks in the tank. While many people just fill the tanks with water, even the tiniest pinholes won’t always leak under these conditions.

Later, the gasoline tanks are placed, only to stink like fuel and drip slowly due to a little leak that was not detected by the water. Drilling a small hole and applying pressure to the tank is the best way to do it.

Any breaches will be seen instantly when a little soap and water is applied to the welds. If you don’t want a disaster in the aluminium marine fuel tank fabrication project, do not skip this step.

8th step: Fuel tank installation or mounting

Ensure that the tank is firmly attached to the vehicle and that it will not rub or come into contact with anything. If you plan on utilizing the vehicle in a sanctioned event, make careful to check the organization’s requirements for fuel tank/cell mounting and adhere to them. And guess what? You did it! Took us a while but worth it, right?

Tips for Aluminum and Stainless Steel Marine Fuel Tank Fabrication

Here are a couple of useful tips for the fabrication and maintenance of your marine fuel tank.

  • To protect the tank from moisture, you can use a solution like Derlin that helps in mounting the tank to something that isn’t water absorbent. Besides securing the tank, industrial enclosures are of good use too.
  • If your boat has an outdated tank model, it is time for replacing the fuel tank in the boat. Custom dimensions, following standards, and using the right material can help you deal with this.
  • Before you start the fabrication project, remember to consult with an experienced shop for customizing metal applications for durability, fit, and stability.

Frequently Asked Questions

What is the best material for a boat fuel tank?

Although most boats come with a plastic fuel tank, as per the durability and cost-effectiveness, I would say metals like aluminium or stainless steel is the best on the table.

What gauge steel is a fuel tank?

The fuel tank durability also relies on thickness. In the case of steel, the right one is to go for 12 gauge steel or stainless steel of 14 gauge.

What are the two materials used to construct fuel tanks?

The two main materials for fuel tank construction is either high-density polyethene plastic or metals like aluminium and steel. While blow moulding is used to make tanks from plastic, stamped sheets are used for welding fuel tanks in the case of aluminium.

Final Words:

With this, we have come to the conclusion of the article, now you know how to build a boat fuel tank from scratch. Hopefully, it will not take you long to get done with the project with booming results. Just follow the steps correctly and take some time to patiently carry them out. Good luck, time to get your building tools out!

Jack K. Pride
Jack K. Pride

Jack K. Pride is an accomplished author and a prominent figure in the boating community. With a passion for boats and a deep understanding of the maritime industry, he has been sharing his expertise through his compelling articles on OutedWeb.com.

Known for his insightful and informative writing style, Jack's articles provide valuable insights, tips, and knowledge to boat enthusiasts worldwide. His dedication to the subject matter and commitment to delivering high-quality content makes him a trusted voice in the boating world.

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