Does your sailboat work with an engine? Then, the engine needs its food! In other words, the engine has to store and get its fuel in order to make the engine work. Therefore, your engine needs a fuel system. There are two types of marine fuel tanks, the permanent and portable. Inboard or sterndrive sailboats usually have permanent fuel tanks that are located under the deck. As for the portable fuel tanks they can be removed from the sailboat for refueling. Also, smaller outboard-powered sailboats often use portable fuel tanks. It is possible to extend your boat’s operating range by simply adding more portable tanks. So, let’s see some details about the fuel system and then examine the appropriate gas tank size for a sailboat.

Tank Installation

A permanent fuel tank that is buried beneath or behind foam, insulation, fiberglass, timber, or joinery work is particularly difficult to regularly inspect for chafe, damage, leaks, or corrosion. Therefore, the ideal tank installation should have easy access. However, it’s not quite easy to install a fuel tank in a way that all its sides are accessible. Another feature of the ideal tank would include baffles. Baffles are vertical/horizontal barriers or walls within the tank. Baffles are an important feature because they reduce the movement of the fuel within the tank. Also, baffles strengthen and stiffen the tank. So, it’s recommended to install baffling on most tanks larger than 30 gallons, depending on the tank’s shape.

Moreover, we can’t forget to note the importance of plumbing fittings and their attachments. It’s much better to attach to the tank’s body threaded and removable fittings than permanently attached ones. Removable fittings are less damageable, take in different sizes of hoses, and are easy to disassemble in order to clean or inspect them. Finally, because contamination within diesel fuel tanks is almost certain, remember to inspect your tank regularly.

Sailboat Fuel Tank Materials

Aluminum

Aluminum is easy to work with, comparatively inexpensive, light, and corrosion-resistant. However, it’s not at all corrosion-proof. One of its primary weaknesses is its susceptibility to some corrosion, particularly galvanic, pitting and poultice. Poultice corrosion can happen when the aluminum is in continuous contact with a wet surface, such as wood, or stagnant water. In order to prevent this, pay particular attention to the details of its installation.

Stainless Steel

Until recently, this ferrous material was not permitted for tank fabrication, unless the tank was limited to a small size of 20 gallons. Today, ABYC has changed its guidelines and allow the fabrication of stainless steel tanks. One of its disadvantages is that stainless is susceptible to crevice corrosion. This can happen when stainless steel is exposed to oxygen-depleted water for a long time. To prevent constant contact with stagnant water there are certain measures to take when fabricating a stainless steel tank. Moreover, these tanks are particularly expensive in comparison with aluminum or steel tanks.

Steel Tanks

Mild steel or low-carbon was a common material for fuel tank fabrication. They are considered inexpensive and robust tanks. The downside of steel tanks is that they tend to rust easily. Steel tends to rust from the inside surface and retains its basic shape while it gets smaller. Nowadays, there are a lot of boat builders that changed steel tanks to fiberglass in order to extend their life expectancy. In any case, it’s a fact that interior corrosion can attack any metal tank, but with a properly maintained system, you can prevent it from happening.

Fiberglass

Fiberglass was the only non-metallic alternative, before polyethylene. It’s corrosion-resistant and really strong. Above all, it is important to use the proper resin i.e. vinylester or epoxy, as well as a careful meticulous lamination technique. Due to the fact that fiberglass’s installation methods are immune to corrosion, it’s not necessary to isolate the materials from moisture or from bilge water. The only downside of fiberglass is that it can be damaged when exposed to certain fuel additives such as ethanol.

Polyethylene

A popular material for fuel tank fabrication is polyethylene. Sailboat manufacturers like Hunter and Beneteau use polyethylene fuel tanks. Also, many other manufacturers use these tanks on gasoline-powered powerboats. The advantages of polyethylene tanks are that they’re strong, corrosion-proof, light, and inexpensive. On the other hand, because the tanks are roto-mold the installation of full internal baffles is not possible. Furthermore, chafe is another problem with polyethylene tanks, as it is for most tanks. Finally, keep in mind to pay attention to poly tank installation because of their tendency to hydrocarbon expansion.

Sailboat Gas Tank Size

The sailboat’s gas tank size depends on various factors. Firstly, the type of your sailboat, its size, its age, among others. Every vessel usually has a permanent fuel tank below the deck with lines that run to its inboard or outboard engine, regardless of the engine’s type. Did you know that water is the enemy of your fuel system? When there’s water in the engine’s fuel system this can lead to corrosion and thus to engine breakdown.

So, how to measure your fuel tank size? Firstly, if you can get to your tank, measure it, (length X width X height) into cubic feet or inches and then convert the result into gallons. There’s no need to run your tank dry. Another suggestion would be to locate the plate/placard on your tank that will tell you its capacity. Another important factor to consider is the consumption rate per hour of cruising. Note that many catamarans have larger tanks because of their large size. A large 40 feet catamaran would normally have 250-300 gallons fuel tank capacity.

Here Are Some Popular Sailboats and Their Tank Sizes

  • A sailboat with a 35 HP engine will normally use 60 gallons (227 liters).
  • A Hunter 420 with 60 gallons will provide approximately 400NM of cruising.
  • A Hunter 33.5 with a Yanmar 2GM engine has a 22 gallons gas tank and cruises for approximately 50 hours.
  • A 43 feet Gulfstar with 65 gallons capacity, can cruise for approximately 80 hours.
  • A Beneteau Oceanis 400 has a 40-gallon gas tank capacity.
  • A Lagoon 389 has a 68-gallon gas tank capacity.
  • An Island Packet 40 has a 90-gallon diesel tank.
  • A 47 feet Catana 471 has 211 gallons of gas tank capacity.

Average Sailboat Fuel Tank Size – Summary

As you can see, the average sailboat fuel tank size is 40 gallons. However, as mentioned before, gas tanks are made from different materials and their size depends on few but important factors. The type of your sailboat, its size, its model, and if your sailboat is new or old. In addition, in order to measure your gas tank size, there are two simple ways of doing it. The first way is to measure your tank’s length, width, and height, in inches or cubic feet, and then convert the result to gallons. The second way is to find the placard on your tank where you will find the exact capacity of gallons for your fuel tank system. Last but not least, your sailboat’s fuel system is essential for the engine’s functionality. That’s why you have to remember to regularly maintain your sailboat’s entire fuel system in order to prevent any costly repairs.