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Safety standards for gasoline fuel systems on recreational boats.

The EPA regulations cited below are now in effect. They became effective January 1, 2012 and all boat builders and boat importers must comply with them. 

Ethanol and Blended Fuels:  In recent years the US EPA has required use of Ethanol blends in gasoline. E10 (10% Ethanol) was the standard, but in 2010 and 2011 the EPA began looking at the use of E15 (15%). The marine industry raised strong objections to this and as of 2012 E15 use is limited to road vehicles produced after 2007.  It is not recommended for use in marine engines.  Here are some references:

Survey Of Published Data And Reports On Blended Fuels In Marine Applications:  US Coast Guard.

Hottopics: The latest on Ethanol And New Research On Isobutanol

Much Ado About Ethanol


Warning; I am only going to very briefly cover the basics here. There are requirements in the Federal Regulations and in ABYC standards that are not included here! I will only hit the high points. Contact ABYC and the Coast Guard to get the latest standards for fuel systems.  Read the Federal Regulation 33 CFR 183.501-183.590. Federal regulations for recreational boats apply only to gasoline, but I have included notes when the rules for gasoline differ from the ABYC standards for diesel.  ABYC has standards for both permanently installed gasoline fuel systems. and portable fuel systems.

Diesel Fuel Systems: The USCG does not regulate diesel fuel systems for recreational boats.  However, ABYC does have a standard for Diesel Fuel Systems in ABYC H-33.  Contact ABYC ( for a current copy. There are also ISO ( ISO 10088 can be obtained through ABYC) and Canadian Standards ( for Diesel Fuel Systems.

First a note about the reasons behind the fuel, electrical and ventilation standards. Why is all this stuff required?

Safety Considerations for fuel systems.

A page about Marine Engines 

The Federal fuel system safety standards in 33 CFR 183.501-183.590 apply to:

Recreational Boats with permanently installed inboard gasoline engines for:



Auxiliary Equipment

This does not apply to:


Portable Equipment: (portable means it can be removed without using tools)

Although you aren't required to follow the Federal fuel system regulations on outboard powered boats, you should use them anyway. Better yet, use the ABYC standard which is more comprehensive than the Federal standard. ABYC standard H-24 Gasoline Fuel Systems applies to both inboard and outboard powered boats with permanently installed fuel systems.   If you ever get dragged into court, the complainants attorney will ask you. "Do you meet ABYC standards?"  If you decide to use portable fuel tanks, ABYC has a standard, H-25 Portable Gasoline Fuel Systems, for boats with portable fuel tanks.  They also have a standard for diesel fuel; H-33 Diesel Fuel Systems.


I strongly recommend that anyone building boats with permanently installed gasoline tanks not build their own tanks. The reason is simple. You have to certify that whatever you put in this boat meets Federal Regulations. Fuel tanks have to meet a whole raft of rules, both USCG and US EPA, and unless you are setup to test them it's better to just buy them from someone who has already tested and certified the tank. 

The same logic applies in other countries that use the Recreational Craft Directive, or the ISO standards.  It is much easier for a boat manufacturer to buy tanks from a tank manufacturer who certifies that the tanks meet the standards that apply in that country, than it is to build your own and go through the lengthy and expensive certification process.

Here's a list of the USCG tests that tanks have to meet. See 33 CFR 183.501-183.590

The 2 minute fire test: Under very specific conditions the tank has to survive a fire for 2 minutes. The test setup for this is not cheap and only a few test labs have one and know how to perform the test.

Slosh Test:

Pressure Impulse Test:

Static Pressure Test:

The tank must be capable of passing all of these tests. If it passes the Static Pressure test it must have  a label that says; "This tank has been tested under 33 CFR 183.580" which means it has passed the static pressure test. There is more information that needs to be on this label. See labels

Also, if you are planning to put the tank in the forward half of the boat it has to meet additional requirements. Tanks that don't meet those requirements have to have a label saying "Must be installed aft of the boat's half length."

Gasoline tanks cannot be integral with the hull. That means that the hull cannot form one side (or more ) of the tank. Tanks must be separate from the boat structure. and cannot support a structure or deck. Some boat builders do use integral tanks but only on diesel powered boats. Diesel fuel tanks may be integral with the hull.

Additionally, plastic (cross-linked polyethyelene, roto molded) tanks have to meet EPA requirements for evaporative emissions and be labeled by the tank manufacturer.

So, go buy a tank from a tank supplier.

Some other considerations. Basically there are two kinds of tanks commonly used in recreational boats, aluminum and plastic. Both have distinct advantages. Some people swear by aluminum, others swear at it. The same is true for plastic. I prefer plastic. Plastic tanks don't corrode. But the choice is yours to make. Tanks are occasionally made out of other materials such as steel, stainless steel, monel and so forth. If you want to use materials other than aluminum or plastic, you will probably have to have the tank specially made. No matter what material they are made out of they all have to meet the same standards for strength and fire resistance.

Some builders want to build tanks out of fiberglass reinforced plastic (FRP).  This is common practice for diesel tanks but not advisable for gasoline tanks. It is not prohibited, if they meet all the other requirements for gasoline tanks.  But, there have been serious problems with FRP gasoline tanks leaking, primarily due to high levels of ethanol (ethyl alcohol) in the fuel.  I would strongly recommend you do not make gasoline tanks out of FRP.

Prohibited Materials:

Ternplate: (Sheet steel, coated with a lead-tin alloy. An alloy of lead containing tin (10-20 per cent) and antimony (1.5-2 per cent.)

Black Iron or Carbon Steel:  Unless galvanized on the inside and outside.

Ferrous materials encased in foam:  If you want to enclose a tank in foam the tank cannot be a tank made of a ferrous (iron or steel) material.

To see all of the standards for tanks call the American Boat and Yacht Council , (410-990-4460) and get a copy of H-24 Gasoline Fuel Systems, or H-33  Diesel Fuel Systems.

The rules for plastic fuel tanks have changed. The US Environmental Protection Agency (EPA) has published evaporative emission requirements for fuel systems on recreational boats.  When purchasing plastic tanks be sure to ask your supplier if they meet the EPA standards.

Here are some links to explain the Evaporative Emissions Regulations from the EPA.
USCG and EPA Guidline for fuel systems

EPA Documents on Evaporative Emissions Regs
Perko Evaporative Emissions

Fuel Tanks An article I wrote for Pacific Yachting Magazine Published January 2009 (in PDF Format)

Fuel Tank openings: Any opening in gasoline fuel tanks must be on the topmost surface of the tank. The fuel inlet, the fuel tank vent, the opening for the level gauge and the opening for the pick up must all be on the topmost surface of the tank. 

Prohibited openings: Drains are not allowed. Sight gauges are not allowed.

Diesel tanks are allowed to have openings below the top of the  tank such as a drain, or sight gauges.

Foaming in Fuel Tanks: (encasing the tank in plastic foam)

Sec. 183.552 Plastic encased fuel tanks: Installation.

(a) Each fuel tank encased in cellular plastic foam or in fiber reinforced plastic must have the connections, fittings, and labels accessible for inspection and maintenance.

(b) If a metallic fuel tank is encased in cellular plastic or in fiber reinforced plastic, water must not collect between the plastic and the surface of the tank or be held against the tank by capillary action.

(c) If the plastic is bonded to the surface of a metallic fuel tank, the adhesive strength of the metal to the plastic bond must exceed the cohesive strength of the plastic.

I believe that foaming a metal tank in place is a death sentence for the tank. Why? Because the foam traps moisture between the foam and the tank. It is that simple.  Some builders like to foam tanks in place.  It is simple, cushions the tank against impact, and they don't have to build a complicated mounting system for the tank. However, consider the consequences.

The US Coast Guard requires that if you foam a tank in place the strength of the bond of the foam to the tank must be stronger than the foam itself. In other words,  a shearing force would break the foam before breaking the bond.  In practice this is very difficult to achieve.  What happens in reality is that after repeated slamming of the hull, and vibrations from the engine, the bond breaks. This creates a gap between the tank and the foam, and moisture gets trapped around and under the tank.  Further,  the requirements for tank installation are,  no moisture can be trapped on the top of the tank, and the fuel fittings must be accessible.  This means if  you foam the tank you must leave an area clear of foam around the fittings, or not allow any foam above the top of the tank.  Otherwise any moisture on top of the tank gets trapped there by the foam.  In practice the above requirements are rarely achieved and the tank corrodes long before its normal life span.

Also consider aluminum tanks.  Aluminum tanks are rarely painted because they have a natural aluminum oxide coating that is formed by exposing aluminum to air.  This oxide protects them from corrosion.  So aluminum tanks should always be mounted with space on all sides and the bottom. To paint aluminum or to bond foam to it,  you must remove the aluminum oxide.  You are removing the very thing that protects the tank from corrosion.

Plastic tanks on the other hand do not need coatings or paint.  They need to be installed so that they will expand a little when first filled. Foam would not allow this expansion. Additionally foam will not adhere well to polyethylene plastic, so it is impractical to foam in a plastic tank. 


Vents: Fuel tanks have to be vented. The vent itself has to either have a flame arrestor that can be cleaned, or be designed in a way to prevent a flame front from igniting the fumes in the vent. There are a lot of different brands of fuel vent fittings on the market that accomplish this. Some times the vent line itself can be a flame arrestor. This depends on the design of the vent.

The US EPA rule would require charcoal filters on vent lines.  Check with the USCG or ABYC.  (The links below are not an endorsement of Perko, Attwood or BlueSkies. It only illustrates the system with a charcoal filter.)

Perko Evaporative Emissions

In addition canisters must not get water or liquid fuel in them because it ruins the contents and makes them unusable. So there must be some means in the vent line to prevent water intrusion. The following items are methods that can be used. There are other solutions.

Perko's Water Deflector vents

This vent must not allow gasoline that might spill from the vent when someone overfills the tank, to spill into the boat. However, it is also illegal to spill fuel into the environment. So, think about it. There are several manufacturers that make combined fuel fill and vent fittings that do just that.

Fuel hose must now meet much stricter standards for evaporative emissions.  Look for hose labeled USCG Type A1-15, USCG Type B1-15.  This means it meets the new EPA standard.

Fuel Hose: When fuel hose is used it must be either USCG Type A1-15, USCG Type B1-15. Where you use it determines what type you use.

From the fuel inlet on the engine (usually the fuel pump) to the carburetor you must use Type A1-15.

 Each fuel vent line or fill line must be USCG Type A1-15 and the line from the fuel tank to the engine inlet must be type A1-15;


if no more than five ounces of fuel is discharged in 2 1/2 minutes when:

(A) The hose is severed at the point where maximum drainage of fuel would occur,

(B) The boat is in its static floating position, and

(C) The fuel system is filled to the capacity market on the tank label.

Then you may use Type B1-15.

As a practical matter, few boat builders want to have to stock two types of hose, so most buy only Type A1 and use it everywhere. This is fine. Just be sure that you put in your owner's manual that the hose from the fuel pump to the carburetor and the vent and fill hose must be TYPE A1-15.

So what is the difference between A1, and B1. USCG Type A hose has to pass the 2 minute fire test, B does not. The theory is the A is under more pressure than B, and being on the engine is exposed to more danger of fire than B. Since B is between the pump and the tank, if a leak occurs, the pressure rapidly drops to zero and the pump just sucks air, stopping the engine. Fuel doesn't get sprayed all over the place. The fuel line between the fuel pump and the carburetor, or fuel rail, is under pressure and if a leak develops, fuel will be sprayed around the hot engine. So there is a greater risk of fire. This hose must be A1-15 which is fire resistant. In addition, A1 hose is required when the hose always has fuel in it. Hose that only has fuel in it briefly, such as the fuel fill hose may be B1.

You do not have to use hose! You can use metallic lines. Some manufacturers do. For example, Mercury Marine inboard engines come with steel fuel line from the fuel pump to the carburetor. Metal lines do not allow vapor to escape through the fuel line walls.

Metallic fuel Lines: If you use metallic fuel lines, the ones that run from the fuel tank to the fuel inlet on the engine must be one of the following; seamless annealed copper, nickel-copper, or copper-nickel. From the fuel pump to the carburetor they can be any metal you want to use. Beware. You could set up a galvanic couple and the tube will be eaten away like powder. Choose carefully if you use metal fuel line from the pump to the carburetor.  Do not use copper tubing. Pure copper is very subject to galvanic corrosion and cracking from vibration.

Anti-Siphon: The fuel line on a boat must run uphill, or else you have to have an anti-siphon device. An Anti-Siphon valve is that annoying little valve that most builders put at the tank outlet, that seems to get clogged at the most inconvenient times. So, if the top of the fuel tank is higher than the inlet on your fuel pump you have to put anti-siphon in the system. This is because the possibility exists that your entire fuel tank could siphon out into your carburetor, and fill up your manifold, and ruin your whole day! So, the solution is obvious. If you don't want this nasty little gadget in the fuel line, put the tank lower than the engine fuel inlet.  But, also make sure none of the fuel line between the tank and the fuel inlet on the engine dips below the level of the tank top.

System Pressure Test: The entire fuel system must be pressure tested to insure there are no leaks. You have to test the system at least at three PSI, unless you have a long deep system. Then it must be 1 times the greatest pressure in the lowest part of the system. For most boats three PSI will do.

Grounding: All metallic components of the fuel system that are in contact with fuel must be electrically grounded to prevent a static discharge from causing a fire or explosion.

Recent events have caused the boating industry to examine the policy regarding the bonding of plastic body fuel fills with metallic caps and retaining chains.  Existing USCG & ABYC policy states that the bonding of these components is voluntary.  A study by IMANNA Laboratories has shown that connecting the metallic retaining chain and cap of a plastic body fuel fill assembly to a boats bonding system may result in electrostatic discharge from a land-based fuel pump nozzle to the metallic components of the assembly when the boat is not in the water.  This condition does not exist when the boat is in the water due to the equalizations of the ground potentials between the fuel pump nozzle and the boats bonding system. 

It is recommended by ABYC and the USCG that new and existing installations of this type of fuel fill assembly DO NOT INCLUDE any attachment to the boats bonding system. Existing connections should be removed from the point of connection to the boats bonding system to the fuel fill assembly.  Removal of the metallic components of the assembly is not necessary; however, the U.S. Coast Guard and ABYC still require that METALLIC body fuel fills be bonded. 

For further information contact:

John Adey, ABYC (410) 956-1050 ex, 29

US Coast Guard at 202-372-1077

Fuel Hose

A typical fuel tank installation showing fill (red hose), vent and fuel line to engine (center). The fitting in the upper right corner is the fuel gauge sender.

Type A Fuel Hose

Type A1 Fuel Hose (Blue Stripe) and Type A2 Fuel Hose (red Stripe) (A2 no longer used)

A diagram of a typical fuel tank setup for a single tank - Prior to January 1, 2012 (Click on the image for full size)


33 CFR Subpart I: Fuel Systems  USA Recreational Boat Fuel System Regulations

TP 1332: CONSTRUCTION STANDARDS FOR SMALL VESSELS Section 7 Fuel Systems Canada Standards for small craft.

Fuel system diagram
For Gasoline Fuel Systems on Recreational Boats Made or Imported into the United States After January 1, 2012,  EPA Compliant Fuel System

See ABYC Standard H-24 Gasoline Fuel Systems
Moeller Marine Products Custom Tank Design. Pdf shows the design of a gasoline fuel tank.
New Fuel tank

Inspected Vessels:

For manufacturers/builders building small passenger vessels that are inspected and certified by the US Coast Guard, there are regulations for their fuel systems different than those for recreational boats. 

46 CFR Subchapter T Part 182 Machinery Installations Subpart D: Passenger Vessels under 100 Gross Tons.  USA Fuel System Standards for Commercial Small Passenger Vessels. Under 100 Gross tons. 

Carburetors: Carburetors must be of a marine type. Again this is because you don't want fuel spilling into the boat. So, if the carburetor floods or the float sticks it must be designed to keep the excess fuel from flowing out of the top of the carburetor through a vent or other opening. Use only a marine type carburetor! Yes, they cost more. Yes, they look just like an automotive carburetor. But, they are different inside, and the difference can save your life. See Marine Engines 101

Flame Arrestors: See Title 46 CFR Chapter I Part 58 Internal Combustion Engine Installations

33 CFR 183.505:  Flame arrestor means a device or assembly that prevents passage of flame through a fuel vent.

Marine Carburetors and Fuel Injection systems must have a flame arrestor installed to prevent a back fire from igniting fuel vapor in the engine compartment. If the air induction system is in itself a flame arrestor, or if a backfire would be directed outside the boat and away from the passengers or interior of the boat then the flame arrestor is not required.  Some fuel injection systems and ram air induction systems meet this last part, but most don't.  If you are worried about the engine getting enough filtered air, there are flame arrestors on the market that also act as filters. Here is an example:,%20Filter,%20Flame%20Arrestor

This is a safety regulation that has been around since the Motor Boat Act of 1940. Marine gasoline engines have not always been as sophisticated and reliable as they are now, and were often going out of tune. So a means was needed to prevent explosions from engines that backfired. Here are examples of typical flame arrestors, one from my own boat, a 1972 Sea Ray, and a modern unit.

Flame Arrestor Gaffrig Flame Arrestor

Prior to 1991 Flame Arrestors had to be USCG Approved.  But since there are excellent industry standards for flame arrestors the U S Coast Guard changed the requirement so that you could use either USCG approved units or those that meet SAE or UL standards.

(3) The following are acceptable means of backfire flame control for gasoline engines:
(i) A backfire flame arrester complying with SAE J-1928 or UL 1111 and marked accordingly.

Fuel Pumps:

Fuel pumps must be mounted on the engine or within 12 inches of the engine.  This is to keep the amount of pressurized fuel line as short as possible.  It is a bad situation to have long fuel lines that are under pressure snaking through the boat. If you get a leak they will dump all of the contents of the line into the boat.  The shorter the line the less fuel that will be spilled. 

If they are not mounted on the engine they must be securely mounted to the boat structure to prevent and they cannot put any strain on the fuel line.   Fuel pumps cannot be supported by the fuel line.

Fuel pumps cannot leak into the boat, so if you have an engine that uses a mechanical fuel pump it has to be a double diaphragm pump or have some other means to keep the fuel from leaking into the boat. The pump must be capable of passing the 2 1/2 minute fire test.

Electric fuel pumps can only operate when the engine is running.

The exception to this is on fuel injected engines.  Fuel injected engines require the line to the fuel rack to be pressurized for the engine to start.  So the pump is allowed to come on momentarily to pressurize the line.  This is not the entire fuel line, it is only the line from the pump to the fuel rack. Then the pump shuts off until the engine starts.

Fuel Stop Valves: (shutoff valves) They must meet the same fire test as other fuel fittings.  If they are electric they can only operate when the ignition switch is on and they must be able to be operated manually.

Fuel Filters and Strainers:

Filters and Strainers must also be capable of passing the 2 1/2 minute fire test. They must be securely mounted on the engine or boat structure.  This mounting must be independent of the fuel line. In other words, the filter or strainer can not be putting any strain on the fuel line.  The only exception is a filter inside a fuel tank.

Seals and gaskets in fuel filters and strainers:

b) Each gasket and each sealed joint in a fuel filter and strainer must not leak when subjected for 24 hours to a gasoline that has at least a 50 percent aromatic content at the test pressure marked on the fuel tank label.

To put it simply, these seals and gaskets must be resistant to gasoline, and that includes gasoline with ethanol.

Clamps: If you use clamps, they must be used with hose designed for clamping. Sounds pretty obvious doesn't it. They must be placed beyond the bead, flare, or over the serrations of the mating spud, pipe, or hose fitting; and, not depend solely on the spring tension of the clamp for compressive force. Again this is pretty obvious stuff. In addition, the law doesn't require it but ABYC standards and good practice require that clamps be at least inch wide, and each hose should be double clamped.

A clarification: The USCG regulation says that hoses on the fuel fill system must be double clamped, but they are silent on whether or not the vent line must be double clamped. The rule has always been, if it's not prohibited or required then it's allowed.  So vent lines may be single clamped. The ABYC standard H-24 Gasoline Fuel Systems, only requires the vent to be single clamped.  But I have always recommended double clamping.  It is just as disastrous to have a vent line come loose, as it is for a fill line.

Clamps must be a corrosion resistant material. Use 316L stainless Steel. But be careful. Many stainless steel clamps do not have stainless steel screws that tighten them.  Make sure you specify that the screw be stainless also.

Some hoses are not designed for use with clamps. For instance Aeroquip racing hose has permanently installed end fittings. You do not use clamps with these hoses. 

Fuel Fittings: If you don't use clamps, but use fittings instead they must be:

A swaged sleeve;

A sleeve and threaded insert.

Accessibility: This is self explanatory.

Sec. 183.554 Fittings, joints, and connections. Each fuel system fitting, joint, and connection must be arranged so that it can be reached for inspection, removal, or maintenance without removal of permanent boat structure.

Revised 10/03/2018 2012-01 All rights reserved.