
What is causing the rise in outboard fuel line problems? We’ve had problems with two hoses in the past three years.
RECOGNIZING THE PROBLEM
A blocked outboard fuel line prevents fuel from getting to the motor. It generally starts with a partial blockage, where playing around with the fuel hose and pumping the primer bulb will get the motor to start or keep it running. But blockages don’t cure themselves. In a few days, squeezing the primer bulb does less and less, possibly getting to the point where there is no resistance in the bulb and it does not expand when released.
When this happened to us recently, the solution was pretty simple: a new hose.
PICTURES OF THE BLOCKAGES
I was curious about what had happened – both basic curiosity and wanting not to have continued problems.
Dave, my husband, began by trying to blow through 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:

But the second one looked a little funny:

It looked like the inside of the hose had melted and twisted.
Turns out, these new hoses have a “non-permeable liner.”

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:

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:

WHAT IS HAPPENING TO THE HOSES
In talking with clerks at the local NAPA store, West Marine, other cruisers and outboard mechanics, it seems that we are not alone in our outboard fuel line problems.
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 of the hose, 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 a 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 its own, but you need to be careful not to add to the problem.
OUR SOLUTION
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. Either type of hose can have a problem.
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Carolyn Shearlock has lived aboard full-time for 17 years, splitting her time between a Tayana 37 monohull and a Gemini 105 catamaran. She’s cruised over 14,000 miles, from Pacific Mexico and Central America to Florida and the Bahamas, gaining firsthand experience with the joys and challenges of life on the water.
Through The Boat Galley, Carolyn has helped thousands of people explore, prepare for, and enjoy life afloat. She shares her expertise as an instructor at Cruisers University, in leading boating publications, and through her bestselling book, The Boat Galley Cookbook. She is passionate about helping others embark on their liveaboard journey—making life on the water simpler, safer, and more enjoyable.
Bob Burnham says
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 says
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.
Josh Carpenter says
Tygol lines. That’s the material they make small fuel lines out of now for like weed Wackers, and what we replace everything on seadoo’s with, especially oil injection lines. They have about a 2 year life expectancy, and generally that’s because they become brittle, but they never gum up and they’re a single material that’s translucent so you can verify flow. OEM lines absolutely DO NOT work correctly for anything older than 00. The ethanol eats the hose from the inside and makes a green gel/goo/slime that gets trapped in all the various filters. You’ll start noticing a slight sputter or miss at idle, but she’s fine at WOT.
Chris Munson says
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 says
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 says
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!).
Hans says
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.
Dave Skolnick (S/V Auspicious) says
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.
John says
Great article
Larry Whited says
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 says
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 says
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 says
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 says
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.
Edwin Lugardo says
Clean your vst tank take it apart
Diana K Weigel says
Even more issues caused by mandated ethanol. Thanks for the information.
Dawn Read says
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 says
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 says
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 says
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.
S/V Viva says
The cover on double braid polyester rope can be used for UV protection.
Anonymous says
Louis Maconi mine was probably too old to have this issue, but who knows.
Anonymous says
I think it very likely could have been the problem. A quick Google search shows these fuel lines were made in response to the ethanol mandate in 2005, and have been on the market since at least 2007. I think it’s very likely that motor had one.
Anonymous says
someone else’s problem now…sigh…
Anonymous says
Funny, I think of ethanol as a “new” problem. Not so new now.
Anonymous says
How about pool noodles (and zip ties) to cover the line?
The Boat Galley says
Sure as long as you’ve got that much room.
Harland Harris says
Pool noodles deteriorate fast, shedding plastic to the sea. The outer layer of yacht braid makes good protection, as noted earlier. Heat shrink tubing is a good look.
Anonymous says
Brandon West, these people have a good blog
The Boat Galley says
Thank you! Made my day!
Jacinthe says
Thank you thank you for this post! It put me on the right track and I believe I’ve solved my problem. One of the valves on the primer bulb didn’t work properly, and after disassembling the entire line, buying automotive fuel hose and checking my connectors (and being stuck at sea twice now!) found this simple fix that my mechanic didn’t check properly. I knew the outboard ran well, when it would run, but as soon as it started, it died in the following seconds.
Thankfully, I also had pretty much every thing in my dinghy ditch bag that your post about that mentions too.
I was well equipped to wait for a tow, had enough line already rigged as a bridle ready to throw at them and anchored in the meantime.
Started following you after Totem mentioned you and I love what you do.
Many thanks,
Jc
Carolyn Shearlock says
So sorry to hear about your problems but very glad that you found it helpful! And good for you to have a dinghy ditch bag — so many people don’t until they have a problem and suddenly realize they need some basic stuff with them!
Bill MCBurney says
Wally World Wood hoses are ok if you change then every year. just dont forget.as they will only last
a a season or two tops, like there Stanley tools.
Capt. Nemo says
I’d say you have an EXCELLENT blog! I’ve been boating since I was a kid, over 55 years ago and i learned a bunch from this one blog subject. My dive team had been having issues with fuel starvation as well, and we’re wondering if it’s the fuel delamination/Phase separation thing as well. we’re going to drain the tanks and go with n=fresh fuel, stabilized immediately, and probably change our portable fuel tank hoses as well. Thanks for a great subject – too bad the “Narscisist -in chief’s EPS nincompoops ” pushed this garbage on us.
Carolyn Shearlock says
Thanks so much. Yeah, I’d definitely at least check your fuel hose. You may be really surprised at what you find in there — yuck!
Ron Pyle says
Yes this sound very likely my problem ill start by redoing my lines thanks
Steve says
I’m having the same problem with my 2000 Yamaha 230 outboard. Motor runs great but after 30-45 minutes just cuts off. Noticed the primer ball is deflating. Replaced the water separator and primer ball and it ran fine for a day then back to cutting off and the ball deflating. I’m no mechanic, but I’m going to replace the pick up line. In the tank and all the fuel hoses/clamps and fuel water separator. Hoping that does the trick. If that doesn’t do it off to the mechanic it goes. Any helpful tips? Do I need to wrap the threads on the tank fitting when replacing? If so what should I use? Nice thread, thanks!
Chris Munson says
Make sure the fuel tank vent is clear, sorta sounds like you’re pulling a vacuum and getting fuel starvation.
Marshal says
Finding this page could save you so much time!
Same problem on my 80s Merc 9.9 (9.8 ?) with a bad old hose from the 80s. It gelled up inside and the carb needed to be cleaned.
Replaced with an overpriced Atwood “Kit” with no ends (how stupid is that) but problem solved, for now.
I’m going to make an automotive line and keep another line as backup. Out of the sun. Ethanol rotted the fuel lines on my truck in 3 years.
Harland Harris says
Is it possible the gasoline gelled. And not the hose? How long did the gas sit in the hose? Did the gas gell in the carb?
Gerald says
Have a 40hp Johnson starts fine but bogs down when giving it throttle! Any suggestions?
DJ says
If using automotive line, what primer bulb would you all recommend? Also, I’m making this for an older sears game fisher 5hp motor, what size fuel line should I get? Thanks
Carolyn Shearlock says
You can get primer bulbs at any marine store — just get one sized to your fuel hose.
Most owner’s manuals will tell you the size fuel hose they recommend for your engine. Generally, for an engine that size, it’s either 1/4″ or 5/16″
Ray Byrd says
I have problem bulb starts to pump up then goes flat and will not expand.I replaced bulb new hose and both ends but problem persist any help . This is a 60 hp evinrude
Carolyn Shearlock says
Is the tank vent open? Have any bugs gotten into the vent to stop it up?
Then check the pickup tube in the tank — make sure there are no blockages.
Paul Greier says
This is a great blog. I have been fighting a similar problem. Only several entries above mention the possibility of a clogged or closed fuel tank vent, which would seem to be indicated by my own problem with a 2006 Hurricane boat with 150 HP 4-stroke Honda outboard, I say this because my problem is always an easy start, then good operation at full throttle for a predictable amount of time … and then a stall requiring a re-priming using the bulb. My question is how to locate the venting method which is used on my boat and how to test it. I have initially replaced the fuel line and bulb twice with no improvement. The stall will also occur after a very long idle. Thanks in advance!
Daniel Conti says
I own a 1995 seaswirl stripper i am not getting any fuel to both squeeze balls changed the anti syphon valve and changed out the water separator still no gas coming to the motors any suggestions also changed both fuel balls and lines at motor.
Carolyn Shearlock says
If you’re not getting fuel to the squeeze balls, I’d look at the pickup tube in the tank. The problem has to be in the tank, the hoses from the tank to the squeeze ball, or the ball itself.
Ken G says
Just replaced fuel pump and all fuel lines. Line from tank to motor (90hp mercury) completely clogged with this yellow/green grainy stuff. Fuel pump inlet clogged at “in” and 50%+ inside pump. Anyone know what this stuff might be?
Carolyn Shearlock says
Sounds like algae that has grown in water mixed with fuel.
Michael Wilburn says
Unfortunately automotive fuel line is NOT a viable solution to this problem. I tried it myself. There are several reasons, but these are the biggest of them. 1 – Automotive fuel hose is NOT approved by the USCG. If you got inspected, you’ll get a polite invitation (or court order), during the hearing for the ticket they write you, to Coast Guard Boater Safety School (AKA Boater Time Out). 2 – Automotive fuel hose works on positive pressure, where the fuel pump in the top of the fuel tank pushes the fuel through the hose. Marine fuel hose works on negative pressure (vacuum), where the fuel pump in the engine sucks the fuel into the hose from the tank. Automotive fuel hoses are made to withstand bursting from internal pressure, but they eventually collapse under vacuum conditions. Save yourselves the headache. Buy marine certified fuel hoses.
Ray says
Does anyone know what fitting I need to hook up to the fuel inlet on a South Bend Motor mdl# 6902 and sr#1661?
Nick says
I have a 60 HP Parsun outboard. After one year, we started having fuel lines rip open inside the engine. Multiple times on the high pressure side. No clue why. I changed the fuel cap which seemed to help, but it just happened again 2 years later. Any ideas?