Coast Guard Fuel Hose Requirements: USCG Type A1 vs. A2
Most boat owners don't think about their fuel hoses until a surveyor flags it or the bilge starts smelling like fuel.
A fuel hose that smells like fuel or has lost its markings won't pass a Coast Guard inspection, a marine survey, or an insurance survey, and it's a fire risk sitting next to your engine. This guide covers Coast Guard fuel hose requirements, the difference between USCG Type A1 and A2, and which hose goes where.
What "Coast Guard Approved" Means for Fuel Hose
Three standards govern marine fuel hose. SAE J1527 is the industry test standard hose manufacturers build to. The Coast Guard's fuel system rules (33 CFR Part 183) say which rated hose can go where on a gasoline boat. ABYC H-24 is the gasoline fuel system standard from the American Boat and Yacht Council, which surveyors and insurers check against, and ABYC H-33 covers diesel.
Every rating measures two things: fire resistance, whether the hose survives a 2.5-minute fire test while full of fuel, and permeation, or how much fuel vapor seeps through the hose wall.
USCG Type A1 vs. A2: Fire Rating and Permeation
The letter tells you about fire. The number tells you about permeation.
Type A1
Type A1 passes the fire test and holds liquid fuel continuously with low permeation (100 grams per square meter per day or less). It's the hose for every line that always has fuel in it, including the run from tank to engine and from fuel pump to engine. Many newer boats use A1-15, a version that meets the tighter EPA and California (CARB) permeation limits.
Type A2
Type A2 passes the same fire test as A1. The difference is permeation, which can reach 300 grams per square meter per day. A2 is meant for fill and vent lines that hold fuel only briefly, such as during fueling, and it can never stand in for A1 on a supply line.
A quick note on B1 and B2
B1 and B2 carry the same permeation classes but skip the fire test. The Coast Guard allows them only where a severed line would leak five ounces of fuel or less in 2.5 minutes. When in doubt, A1 is legal everywhere.
Where Each Fuel Hose Type Is Required on Your Boat
Supply (feed) line: Tank to engine
Hose required: USCG Type A1 (B1 only if it passes the 5-ounce leak test)
Return line: Excess fuel back to the tank
Hose required: USCG Type A1
Pump-to-engine line: Fuel pump to carburetor or injection
Hose required: USCG Type A1, no exceptions
Fill line: Deck fill to tank
Hose required: A1 or A2 (B1 or B2 if it passes the leak test)
Vent line: Tank to vent fitting
Hose required: A1 or A2 (B1 or B2 if it passes the leak test)
The printed marking is what an inspector reads. Approved fuel hose is stamped with its type, such as "USCG TYPE A1." A worn or hidden stamp can fail inspection even if the hose is the correct type.
Ethanol, Permeation, and Why Older Hoses Fail Inspection
Ethanol blends like E10 slowly attack older hose compounds from the inside. Over time, the liner (the inner layer that touches the fuel) softens, swells, or flakes, letting more vapor through and sending debris toward your filters.
Permeation limits have also tightened to keep fuel vapor out of the bilge, where it's a fire hazard. Fuel hose that met the rules when the boat was built may now be well past its limits, and salt and damp only make it worse.
Signs Your Fuel Hose Won't Pass a Coast Guard Inspection
Inspect your fuel system with the engine hatch open and look for:
A fuel smell in the bilge or engine compartment
Soft, spongy, or swollen sections when you squeeze the hose
Surface cracking, especially at bends and near heat
Weeping or dampness at fittings and clamps
Missing, faded, or unreadable SAE and USCG markings
Replace Your Marine Fuel Hose the Right Way with Nebar
Getting the replacement right means matching the correct USCG type and the exact inside diameter for each line. It also means marine-rated fittings, 316 stainless steel clamps, and routing that keeps the hose away from exhaust and sharp edges.
Nebar has been building marine hose in Seattle for more than a hundred years. Bring in the old line or your measurements, and we’ll help you find the right hose for each line, cut it to length at the counter, and fit it with the correct fittings. Before any fuel hose goes on your boat, check the printed marking for its USCG type, and ask us if you’re not sure what you’re looking at.
Take a look at our marine fuel hose and fuel and petroleum hose work, or contact the counter.
FAQ
Do Coast Guard-approved fuel hose expire?
They have no printed expiration date, but fuel hoses do age. Once it cracks, softens, or loses its markings, it no longer meets the standard in practice.
How often should I replace marine fuel hose?
Inspect it every season and replace it at the first sign of softening, cracking, or fuel smell. Fuel hose is commonly recommended for replacement around the ten-year mark, even when it looks fine, because the most damaging damage starts on the inside.
A1 or A2, which hose do I need?
Use A1 for any line that holds fuel continuously, including supply and return lines. A2 is acceptable for fill and vent lines, and A1 works everywhere.