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Safety regulations and standards for gasoline fuel systems on recreational boats.

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

Safety Considerations for fuel systems.

More on Fuel Systems:  33 CFR 183.501-590

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.

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Fuel Pumps: 33 CFR 183.524 and 183.566

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: 33 CFR 183.528 (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:  33 CFR 183.534

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.

When you purchase filters and strainers, or for that matter any fuel system component, check the specifications. Does this item comply with 33 CFR 183.534? Is there a label on the packaging that say it does, or says it complies with USCG requirements? Some filters may have glass bowls, or plastic windows that do not pass the fire test. Never use those plastic in-line automotive filters often seen on older cars. They do not comply with this requirement. I have seen these on boats, usually installed by tbe boat owner. They have been the source of fuel leaks and fires.

Clamps: 33 CFR 183. 532 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 ½ 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 Fittings33 CFR 183.588 If you don't use clamps, but use fittings instead they must be:

A swaged sleeve;

A sleeve and threaded insert.

Accessibility: 33 CFR 183.554 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.


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.

ABYC H-24 Gasoline Fuel Systems

Revised 06/21/2018 © 2012-01  All rights reserved.

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