Interpreting Fuel Hose Rating Designators; Gray Fuel Hose

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
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Interpreting Fuel Hose Rating Designators; Gray Fuel Hose

Postby jimh » Wed Nov 29, 2017 9:37 am

In the USA, flexible hose sold for carrying gasoline fuels is rated with a letter and number system.

The "A" designator means the hose can be used in enclosed spaces, i.e., it passed a 2.5-minute fire test;

The "B" designator means the hose should be used only in open, above deck spaces, i.e., it has not passed a 2.5-minute fire test.

The numerical suffix indicates the suitability for certain applications:

--the "1" suffix indicates the hose is designed to have fuel in the hose all the time, i.e., it has low (less) permeability;

--the "2" suffix indicates the hose is NOT designed to have fuel in the hose all the time, e.g., used for a tank filler hose; i.e., it has higher (more) permeability;

For an authoritative reference, see

For an on-deck, open fuel system, the hose from the fuel tank to the engine can be rated B1, but A1 is better and can be used as well. (On my boat, all fuel lines are rated A1 except the below-deck fuel tank filler hose and the tank vent line.)

All hoses should be clearly marked in plain text as being ALCOHOL RESISTANT. Generally you only find non-alcohol-resistant fuel lines in older boats, made before c.1987.

There is a great deal of field experience with failure of fuel hoses with ethanol-gasoline blended fuels, particularly with fuel hoses having a gray metallic outer jacket. These were common in Mercury installations and were sold by several aftermarket suppliers.

A second numerical suffix of "15" refers to a new rating for ultra-low permeation. This is now required by EPA regulations, and is not a Coast Guard rating.

The USCG safety ratings do not meet the EPA requirements for fuel line permeation, which shall
be less than 15g/m^2/day when tested according to SAE J1527 FEB 2011. EPA-compliant fuel
hose is labeled A1-15 or B1-15 showing the A or B fire rating and the permeation at 15 g/m/day.


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Gray Fuel Hose

Postby dtmackey » Fri Aug 24, 2018 10:48 am

In another discussion on a somewhat tangential topic:

Phil T wrote:Double check the gray fuel line. There have been many many problems with the inner lining degrading and debris entering the engine. I would select Trident or other named brand that is rated alcohol resistant and not gray in color.

I'd like to clear up a misconception on gray fuel line. First of all not all gray fuel line is created equal. I was called out for this on my project Whaler since people tend to think all gray fuel line is the same. Yes, the older gray non-ethanol friendly fuel line was bad and deteriorated from the inside and could cause engine damage, but some of the black fuel lines also had ethanol deterioration as well. I saw plenty black fuel lines where the inner liner would separate from the outer and then collapse leaning out the motor causing damage (on carburetor two-stroke motors). With this in mind, I will not generalize "black" or "gray" fuel line as being bad and feel the responsible thing is to make sure whatever fuel line you use, that it is ethanol compliant and inspect regularly for wear and UV sun damage.

Back in the 1980s and 1990s there were lots of lower-priced gray fuel lines sold that weren't ethanol compliant, that posed no problem until E10 started popping up at pumps around the country. Tempo, among others, sold tons of it. The gray fuel line quickly was labeled as "bad" and many ran into problems and somehow this generalization is still alive today.

Today Trident has both black and gray fuel line. The gray is barrier lined B1-15 rated and ethanol compliant up to E85 (that's 85% ethanol).

[Here I have deleted a picture of text and replaced it with the text. Text should remain text, and not become pictures of text. The text below apparently comes from a vendor's website selling the Trident fuel hose--jimh]

      Trident Barrier Lined B1-15 Fuel Hose is an EPA Approved fuel line for both gasoline and diesel
      Designed for both gasoline (Petrol) (Including ethanol blends up to E85) and diesel (Including bio diesel blends up to 100%)
      Built with best fuel and age resistant formulation
      (2) Spiral reinforcement and unique "Barrier Liner" on inside surface of tube so fuel is not in direct contact with rubber
      Provides extraordinary resistance to fuel permeation and aging, as well as heat, cold, and ozone
      Good bendability
      UV Resistant
      3 Year Warranty

      Cover: CPE rubber
      Tube: Fluoroplastic internal barrier
      Color: Gray
      Tolerance: -20° F - 212° F Temperature Range
      Exceeds SAE J1527, ABYC-24, ISO 8469 B1, USCG Type B1-15
      EPA Certified
      CARB Executive Order for low permeation Type B1-15
      NMMA Type Accepted
      CE certified

Whatever fuel line you decide to go with, make sure you install the proper rated line for your application - above and below deck (enclosed space) fuel lines carry different ratings as well.


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Location: Michigan, Lower Peninsula

Re: Interpreting Fuel Hose Rating Designators; Gray Fuel Hose

Postby jimh » Sat Aug 25, 2018 9:04 am

As pointed out, one sees a great number of instances of unsuitable gray fuel hose in use. While it is now possible to purchase a suitable gray fuel hose from Trident that will work well with ethanol-gasoline blended fuels, I suspect that the great majority of gray fuel lines seen in use are probably the older types which have a substantial history of being unsuitable, and cautionary advice regarding the risk of using them is probably in most instances very appropriate.

To learn that Trident is now making a fuel hose with a gray color that is completely suitable is excellent information to have. Thanks for posting.

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Re: Interpreting Fuel Hose Rating Designators; Gray Fuel Hose

Postby Spc337 » Sat Aug 25, 2018 10:43 am

All of my hoses are Trident. A1-15 from tank to engine (it does travel under the deck for a few feet) replacing some B1 Gray hose from prior owner. A2 1.5" Filler Hose (Couldn't find A1 rated). This is a beast of a hose and just makes the 90deg turn within the space allowed. A1 - Vent Hose.

In my opinion, both the Fill and Vent hose should be A rated. They will hold fuel (less likely on the vent) since there isn't a constant downward slope to ensure drainage once fuel enters the hose. It is spendy stuff but for peace of mind and for the few feet involved, I'm just going with the best I can get.

I'm sure there are reasons that I'm not educated about that would suggest over-specifying these isn't the best idea but I haven't heard of anything yet.
Boston Whaler 1979 V-22 Outrage

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Location: Michigan, Lower Peninsula

Re: Replacing Outrage 22 fuel tank

Postby jimh » Sat Aug 25, 2018 11:06 am

Re fuel remaining in place in some portion of the filler hose, typically rated only for A2 use, that is, to not have fuel permanently in the hose but suitable for enclosed spaces:

I agree that having fuel remain in the horizontal portion of the filler hose than crosses under the deck from the gunwale to the tank filler inlet can be a problem; the permeability of the A2 hose is not designated for having fuel present in the hose continually. For this reason when I am adding fuel to the boat I try to be mindful of this possibility. If we are adding fuel on the water, I try to keep the boat trim so the filler side (the port side on my boat) is raised higher than the other side. You can do this usually by moving a cooler to one side or just sitting on the gunwale on that side.

Once the boat is on the trailer and fuel will be added at a highway filling station, I try choose a pump so that, if there is any grade or slope involved, the trailer is aiming uphill. This helps to get the fuel drained out of the filler. Also, when loading the boat onto the trailer, it could be advantageous to have a slight tilt toward the non-filler side (again, on my boat, the starboard side) so that even when fueling on the highway the fuel tends to run downhill into the fuel tank and not remain in the filler hose.

The worst possible situation with the filler hose is for the hose to develop a dip or low spot in its path from gunwale to tank filler inlet, which then tends to collect fuel no matter what you do while fueling. You might be able to mitigate that problem whenever you get the boat in the water by having a couple of people sit on the other gunwale and get a rather steep list to that side, again encouraging the fuel to flow out of the filler hose. I try to do this when fueling on the water.

The worse situation is to add a lot of fuel for winter storage from a highway filling station with the boat on the trailer. If you then tow the trailer down any sort of big downhill grade, there is a good chance the fuel will move to the forward part of the tank and may rise into the filler hose; it will then sit there for six months of winter storage.

ASIDE: on our old sailboat the fuel tank was located directly below the cockpit deck level. The fuel filler inlet and cap were located on the cockpit deck, and the path into the tank was a straight vertical path. There were two advantages of this: when you added fuel, the fuel flowed directly down a short filler hose and into the tank, so there was no possibility of any fuel sitting in the hose; and, the tank level could be sounded with a stick to get the actual tank level. Because the fuel was diesel, the sounding stick was a smelly old pine dowel that would add a bit of fragrance to the locker in which it was stowed in a small section of PVC pipe fastened to a bulkhead. The other drawback of this arrangement was the location of the filler cap; being on the deck there was always some water sloshing round the deck when you did any cleaning or scrubbing of the deck. The filler cap had to have very good seals to keep the water out of the tank.