Inspecting Your Boat's Gasoline Fuel System

By Michael Hunter

In the case of fire, being part of the "5 percent" is not where you want your boat to be.

Filling powerboat with gasolineAnnual inspection of your boat's gasoline fuel system can help prevent damage to your boat or injuries to you and your passengers. (BoatUS File Photo)

According to BoatUS Marine Insurance files, 5 percent of all boat fires are related to fuel leaks. That likely means that 5 percent could have been prevented with periodic fuel-system inspections. This may not seem like much, until you realize that fires from fuel leaks aren't usually smoky little affairs but frequently involve big, scary flames and all too often result in "explosions." Checking your fuel system on a regular basis may prevent you and your boat from becoming victim to the 5 percent.

In a recent fire investigation, an owner acquired a 10-year-old boat. Like many other boaters, the owner only skimmed over the owner's manual. But in that manual, as well as on a label on the vessel's engine-hatch cover, was a warning label advising annual inspection of the fuel system, something that may have prevented the serious injuries that occurred after the vessel exploded shortly after refueling.

What exactly does that label mean? The American Boat & Yacht Council (ABYC) defines gasoline fuel systems under Standard H-24. By definition, the "fuel system" includes all components originating at the fuel inlet into the hull, its fittings, the filler hoses, its attachments, the tank(s), outlet, and return hoses (if any), and ending at the point of delivery to the engine(s). That pretty much covers everything from the fuel fill on deck to the engine.

ABYC standards represent the collective effort from the entire industry at generating the minimum standards for construction and repair. These are voluntary, but the ones listed under Title 33 of the U.S. Code of Federal Regulations (33 CFR) are not. These are legal requirements. Federal regulations don't appear in a lot of places for recreational boats, but gasoline fuel systems are one place they're prominent. My guess is that the 5 percent was quite a bit higher before these regulations.

The fuel system is directed to have annual inspections. Contrary to public opinion, however, a fuel inspection is not necessarily a mandated part of a winterization, dewinterization, or any other service, unless you specifically request that it be done or the repairer suggests it. I often hear that boat owners are becoming increasingly disgruntled with the perception of repairers "nickel and diming" them on maintenance, and repairers may not suggest this additional inspection. It's up to you to ask, "What else should I be doing?" and to say that you do want a proper fuel inspection by a qualified mechanic.

As a marine surveyor, I'm amazed by how often I find vessels with improper repairs to fuel systems completed by repairers (or owners). Based on my experience, here's my advice.

How To Inspect A Fuel Line

The first part of the inspection is visual. You need to find every bit of fuel line, from the fuel fill to the engine, and verify that the hoses are sound, connections are tight, and hose clamps are in good condition. Run a clean cloth over hoses and then smell the rag. If it smells like gas, the hoses are past their prime and should be replaced. Cracked fuel hoses should be immediately renewed prior to any use. Deteriorated or crushed hoses under clamps should be replaced.

Zip tie replacing hose clampZip ties are not acceptable replacements for steel hose clamps. Fuel was observed leaking from this hose as it enters the tank. (Photo: Michael Hunter)

The best time to check the actual integrity of the system is when you refuel the boat. Follow the proper refueling process. If after refueling you see a leak or spot fuel in the bilge or smell gas, STOP! Get everyone, including yourself, away from the vessel. (They already should be if you're following proper fueling procedures!) Do not activate any switches, which can generate a spark. Call a qualified professional.

Here are some things to watch for while you're doing your own inspection:

  • Aggressive angle between the filler neck to the tank, which routes the hose badly and may cut the hose against the neck causing fuel to leak into the bilge. Note: There should be a green wire (ground) secured to the filler neck and the fuel tank. This prevents static ignition of vapors.

Sanitation hoseSanitation hose, as was used here, is not interchangable with gasoline fuel hose, which is marked Type A-1 or A-2. (Photo: Michael Hunter)

  • A manufacturer, repairer, or do-it-yourselfer can inadvertently install an improper filler neck. Two stainless steel clamps are required at fuel-filler hose connections.
  • Sanitation hose used as fuel-filler hose! Gasoline fuel hoses should be marked Type A-1 or A-2, which meet minimum permeation and fire exposure ratings.
  • Vapor detectors are a great idea, but note that they have a five-year service life from date of manufacture, just like carbon-monoxide sensors. Consult the owner's manual on the recommended replacement interval, or replace if they've ever become submerged.
  • Securing the hose with a zip tie is NOT found anywhere in the 33 CFR or ABYC!
  • Hose-life expectancy varies by elements and exposures and care, but as a guide, manufacturers have indicated fuel hoses that are more than 10 years old should be considered for replacement. Don't simply splice in a new piece; replace the entire hose.

Damaged fuel lineOne of the many problems caused by ethanol-blended fuel is that it deteriorates the inside of fuel lines, as seen here. (Photo: Michael Hunter)

  • Ethanol-blended fuels can wreak havoc on fuel systems. Deterioration of the interior of the fuel lines is common, especially on older hoses. Squeeze lines, and if soft or gooey, replace them.
  • Aluminum fuel tanks and foam are frequently not good bedfellows. Generally speaking, foam prevents the aluminum from producing an oxide layer, which is its protection against corrosion. Trapped water will not drain and results in pitting/poultice corrosion, potentially leaking fuel into the bilge.

In the event you don't have an ABYC Certified Technician at your disposal, a marine surveyor should also be familiar with fuel-system inspection and can be of assistance. Consult with a certified NAMS or accredited SAMS surveyor with ABYC certifications if in doubt.

Understanding ABYC Standards

24.12.1 Flexible hose not equipped with permanently attached end fittings, such as swaged sleeve and threaded insert, shall be attached with corrosion resistant metallic clamps.
Author's comment: This means using real stainless-steel hose clamps, not zip ties. (Yes, I've seen that.)

24.12.3 Hose shall not be installed on helical threading or knurling that provides a path for fuel leakage.
Author's comment: Hoses have to be fitted to a spud, not a threaded pipe.

24.12.6 Clamps shall be beyond the flare or bead, or fully upon serrations where provided, and at least 1/4 inch (6 mm) from the end of the hose.
Author's comment: This just means that hose clamps need to placed on the hose that is all the way on the fitting but not quite at the end of the hose. Leave 1/4 inch of the hose exposed.

24.12.7 Hose used in the fuel tank fill system shall be secured ... by at least two corrosion-resistant metallic clamps with nominal band widths of at least 1/2 inch (12 mm).
Author's comment: Only two systems in the 33 CFR require double clamps: fuel fill hoses and exhaust hoses (good practice also on below-water hose). If this hose comes off, gasoline is going to enter the bilge. Not good! All components of hose clamps shall have a resistance to corrosion equal to or greater than 300 series stainless steel.
Author's comment: Get the best clamps you can find; avoid those from auto parts stores.

Also: If you have a vapor detector in your engine space, know it has a service life (typically 60 months from date of component manufacture) and should be renewed when it ages out or if it is ever submerged. 

Michael Hunter is an accredited marine surveyor, certified marine investigator, and ABYC master technician from Springfield, Missouri.

— Published: October/November 2017

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