The fuel line for our outboard had all the symptoms of a serious blockage. We really weren't prepared for what we found when we cut it apart!

Outboard Fuel Line Problems

Our outboard hasn’t been happy lately. The big problem was that it would sometimes refuse to start (and was not flooded) while other times it would start on the first pull. Many times, playing around with the fuel hose – taking it on and off the tank and the motor and pumping it – would get things going again. To make a long story short, after a few days of that, squeezing the primer bulb did nothing – as in, there was no resistence in the bulb and it didn’t expand again after squeezing it.

In other words, all the symptoms of a blockage in the fuel line.

We got a new fuel hose and Dave transferred the old ends and primer bulb. The engine started right up and the primer bulb behaved normally. Okay, basic problem solved.

But I was curious about what had happened – both basic curiosity and wanting to write a post since others we know have had similar problems.

Dave began by trying to blow though the old hose. He couldn’t in two out of the three sections. That confirmed a blockage. Or actually, at least two blockages.

The first cut end of hose that I looked at didn’t seem to have a problem:

The fuel line for our outboard had all the symptoms of a serious blockage. We really weren't prepared for what we found when we cut it apart!

But the second one looked a little funny:

The fuel line for our outboard had all the symptoms of a serious blockage. We really weren't prepared for what we found when we cut it apart!

It looked like the inside of the hose had melted and twisted.

Turns out, these new hoses have a “non-permeable liner.”

The fuel line for our outboard had all the symptoms of a serious blockage. We really weren't prepared for what we found when we cut it apart!

And it can break free (delaminate) from the outer hose and twist itself up. Hmm, I didn’t see that liner in that first bit of hose that I saw. Wonder where it went? I split the hose lengthwise:

The fuel line for our outboard had all the symptoms of a serious blockage. We really weren't prepared for what we found when we cut it apart!

Hard to get a good photo, but basically the liner appeared to be totally wadded up. No wonder fuel couldn’t get through!

Everywhere we cut, we found a problem:

The fuel line for our outboard had all the symptoms of a serious blockage. We really weren't prepared for what we found when we cut it apart!

In talking with clerks at the local NAPA store, West Marine, other cruisers and outboard mechanics, it seems that we are not alone in this experience.

For the record, this hose was made by Attwood and is not quite 18 months old. We’ve used non-ethanol gas more often than not; when we’ve used gas with ethanol, we used a gas additive as well. I don’t remember the exact designation, but I remember when buying it that it was supposed to be okay for use with ethanol gas.

What I’ve learned (and this is all word-of-mouth and anecdotal):

  • All fuel hoses have more problems than they used to.
  • Ethanol gas causes more fuel line problems but using ethanol-free gas is not a guarantee you won’t have problems.
  • New hoses have an impermeable liner to keep ethanol from degrading the other hose material.
  • That liner can delaminate from the outer hose and cause blockages.
  • The hoses with the grey outside coating (UV protection) seem to have more problems than others.
  • Attwood brand hoses seem to have more problems than some others. They had at least one recall of hoses due to delamination of the inner liner causing blockages.
  • OEM hoses seem to last longer before showing problems.
  • Automotive fuel hose doesn’t seem to be having the delamination problem but doesn’t have the UV inhibitors and may crack from UV damage.
  • When putting hose with the liner on barbed fittings, you have to be very careful that the liner doesn’t separate and “wad up.” It may still do that on it’s own, but you need to be careful not to add to the problem.
Our “solution” was to get automotive fuel hose. Since it doesn’t have the UV protection, we may try to cover the exposed portions of the hose with tubular webbing or even just tubes made from old t-shirts to give it some UV protection. We’re still working on that.

Bottom line, however: carry replacement fuel hose and hose clamps! There is basically no sure-fire method to avoid problems either with the liner or UV damage.

The fuel line for our outboard had all the symptoms of a serious blockage. We weren't prepared for what we found when we cut it apart!

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  • Bob Burnham
    Posted at 11 April 2016 Reply

    My exact same experience with “crap-wood” hoses! They ain’t “worth” carryin’ out of the store–much less the $50.00 they cost (and that’s for their “universal” hose which has no “ends” !”) Thermoid brand hose is American made, u.v. protected, low-permeation, suitable for all fuels (even E-85!) and inexpensive. It’s fabric-reinforced and one-piece construction—no “liner” to collapse and stop fuel flow. E-bay has several vendors.

  • Bob Burnham
    Posted at 11 April 2016 Reply

    About the “automotive” fuel line (hose). I forgot: Thermoid hose is (relatively) cheap @ $17.00 for 25 feet (with free shipping). You can cut a lot of hoses out of a 25′ spool, and don’t have to waste hose since you can cut the length you need for each application. Auto-parts or “small engine” (lawnmower) shops here charge $2.00—$2.50 a foot for 1/4″ or 5/16″ ethanol-resistant line, and I don’t think it’s u.v. protected. 303 will protect it from the sun, and “303” is not greasy. The only “downside” I can think of in using black hose is that it gets very hot in the sun (and will burn your bare buns when you sit on it…) but I’ve bought my last “marine” fuel line (from either “W M”) Besides, the only diameters those sources seem to stock must be for 100+ h.p. engines (3/8″ to 1/2″) and don’t fit small outboard engine fittings. If any of my engines “drank” fuel that fast I would despair of the whole thing! Use “303” (or Armor-All, Son-of-a-Gun or equivalent) on the primer bulb as well for a longer service life since it’s actually vinyl, p.v.c. or e.p.d.m., not rubber these daze.

  • Chris Munson
    Posted at 12 April 2016 Reply

    Great Article!
    On any line older than 5 years, the sun causes the bulb, rubber end connector inserts, and fuel line to age, shrink, harden and crack, leading to tiny air leaks that prevent the fuel pump from pulling gas into the motor, especially at idle. Quick fix: put some grease on the end fittings at the tank and motor. Best to replace the entire line, bulb and connector asap if the engine won’t idle but is OK at higher rpm. Store your fuel line out of the sun.

  • Brian McCue
    Posted at 12 April 2016 Reply

    I would suggest placing the non-uv treated hose within one of those split wire looms that are flexible plastic and split lengthwise. You can keep it closed with either zip ties or electrical tape.

    • Brian McCue
      Posted at 12 April 2016 Reply

      When I was a kid with an a 7 HP Sears outboard engine, the fuel line once split open on me and sprayed both me and the boat with gas. The fuel had pressurized in the tank in the sun (no vent on that tank) and when I turned the handle to steer, the crack finally opened. Lesson – PERIODICALLY check your hoses (and avoid Sears outboards – not really an issue anymore!).

  • Dave Skolnick (S/V Auspicious)
    Posted at 12 April 2016 Reply

    Ethanol is a problem for a lot of reasons, not the least of which is fuel line decomposition, including delamination. Some of those little pieces can end up clogging jets leading to carb rebuilds. Phase separation leaves globs of ethanol in the fuel that the engine cannot run on. The hydrophilic properties of ethanol (any alcohol) draws water right out of the water that builds up in the bottom of the tank and contributes to corrosion of the jets and other parts of the carb.

    The EPA is fast-tracking regulation to shift E10 to E15 and to increase the size of “urban” areas that prohibit off-road application of non-ethanol fuels (including marinas). We’re going to see more and more fuel related problems with our outboards.

  • Hans
    Posted at 12 April 2016 Reply

    I had the same exact problem with an Attwood hose, and it was also gray by the way. It also kinked easier, which led to the engine dying at the most inopportune times, making a bad situation even worse. I will never buy another one of those again. And it wasn’t cheap either.

  • John
    Posted at 12 April 2016 Reply

    Great article

  • Larry Whited
    Posted at 14 April 2016 Reply

    Thanks for the helpful info. Think I’ll spend the money for the OEM and carry an extra. My 30 foot Bolger uses an outboard too. All the more reason for a spare. Thanks

  • cyndy
    Posted at 19 April 2016 Reply

    thank you! I just came by some very small firehose (quite a lot of it) and was wondering what all it could be used for… now it will cover my automotive fuel line that I’m going to change to asap.

  • Edward Gilbert
    Posted at 28 June 2016 Reply

    Just bypassed an inline filter not required by Mercury. The liner caused issues when trying to put serrated coupling in! Folded the liner over and plugged the gas line. Be careful, liner causes issues.

  • Kim Lewis
    Posted at 08 December 2016 Reply

    Question. Being a female I don’t have a lot of engine knowledge. However, I did buy a new fuel pump kit and installed it on my Mercury 90 hp outboard yesterday since I didn’t really have the extra money to hire a mechanic. The lines were full of that lining. I didn’t know what it was at the time I thought it was some kind of gluey nasty buildup. When I give the boat throttle it starves for gas. I replaced all the hoses and fuel pump it still don’t get enough gas to go. What do I do now? Clean out the carburetors? I don’t think I am capable of taking them apart so I’m hoping there is a way to dissolve that lining. I have put sea foam treatment in the tank hoping it will do something for it. Any suggestions would really be appreciated.

    • Carolyn Shearlock
      Posted at 08 December 2016 Reply

      I’m a little confused about what you have done so far. Have you changed all the fuel hose from the tank to the motor. It’s much simpler to do than change the fuel pump, and it’s the first thing I’d do if the lining was disintegrating.

  • Diana K Weigel
    Posted at 02 May 2017 Reply

    Even more issues caused by mandated ethanol. Thanks for the information.

  • Dawn Read
    Posted at 02 May 2017 Reply

    Great article, Lucky Read. Automotive is the way to GO! We’ll find a sleeve of some sort so we don’t end up with a UV problem.

  • Butch Budd
    Posted at 27 May 2017 Reply

    Got duel tanks on my 17 ft Triump Skiff.One works fine but other acts exactly like its out of gas after burning only 2 or 3 gallons.Hose or float?

  • Jacques
    Posted at 03 June 2017 Reply

    I have a fuel issue on my center console. Runs fine at 3/4 speed. But dies off at full throttle. Starving for fuel. Then we can hook up to a portable tank and boat run fine at WOT. Hook back to tank from boat and does the same thing again. Any suggestions. The pickup on the tank is clear also. Fuel line looks ok but I didn’t cut into it. Confused.

    • Carolyn Shearlock
      Posted at 03 June 2017 Reply

      Gotta be between the tank and the engine, then. Is there a fuel filter in there (that you bypassed when on the portable tank)? Check to see if it’s clogged. If not, fuel line is the likely culprit — and in our experience, fuel lines are the most frequent source of trouble, period.

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