Thread: Fuel line size

Amazon has it if you have an account with them. Otherwise most autopart stores should have metric that would be equivalent. Just take a piece in with you to compare with


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I'm by far no expert. But my guess would be if you increased fuel line diameter it would put a strain on your fuel pump because you are lifting a larger amount of fuel

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SHIELDS RUBBER Series 368 Low-Permeation Marine Fuel Hose, Sold by the Foot | West Marine

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Advance Auto Parts - Down for Maintenance

I am in the process of changing out all the fuel lines in my 1992 Astro Bass Boat, some have been in there since new.
Shop around and go back with the same size that you are replacing, but beware of updated regulations regarding fuel hoses per their applications. Generally speaking, these new regulations address changes in fuel, notably ethanol and additives that may not have been in broad use at the time your fuel system was first put in service.
In my instance, my boat has a 20+ gallon fuel tank below the deck. While filling at the pump, I had to fill it very slowly or the nozzle would keep shutting off or worse, gas would splash out early on. The "Fill Hose" connecting the tank to the fuel cap was 1 1/2" X 18" long, was 1992 original, stiff as all get out, deteriorating inside and out, it is now removed and I am awaiting delivery any day now. The new "Fill" hose is special rated, will handle gas, E-85, diesel, or whatever, and has wire strands in it. Next to it is a 5/8" X 18" long "Vent" hose, that was in the same condition, now removed and awaiting delivery. It has a special rating designated to handle occasional fuel, but specially designed to handle fuel vapors.
The remaining fuel hoses are designated generally as "Above Deck" and "Below Deck". Beginning with the below deck hose, it's a Shields Below Deck 3/8" A1-15 Designated Hose that addresses permeation concerns and better flame retardant qualities. In this area, I am also installing a new fuel filter/water separator with the clear bowl on the bottom where I can see the water and drain as needed.
Next is the above deck fuel hose, Shields Silverado 4000 3/8" grey fuel hose, along with a new primer bulb and new quick fuel disconnect at the Mercury 115 Outboard end. They say the grey should reduce heat in the fuel line that could add to issues like vapor lock, and the like.
Many people just use conventional fuel hose from where ever, but there is a difference. Some even use radiator hose for the fill hose, but IMHO, that's just asking for trouble. Safety first!
Oh, and the regs now call for 2 clamps on each end of the fuel hoses.
And I even splurged for a new shiny chrome fuel cap and vent with a internal chain, to replace mine that lost the chain years ago. No more worry about losing that cap anymore!
Here is a video that explains boat fuel hoses, their requirements, and why.
Shields Fuel Hose - iboats.com - YouTube

Originally Posted by huntersdad

I'm by far no expert. But my guess would be if you increased fuel line diameter it would put a strain on your fuel pump because you are lifting a larger amount of fuel

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I think it is just the opposite. The pump is going to work less hard because of the lower resistance from the larger hose.

My plan is to buy the whole kit. 2 connectors, bulb, and hose pre-clamped. It seems that the 5/16 is not as readily available as the 3/8 though.

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Originally Posted by silverside

My plan is to buy the whole kit. 2 connectors, bulb, and hose pre-clamped. It seems that the 5/16 is not as readily available as the 3/8 though.

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Those silver "marine" fuel lines are garbage. They have a clear plastic inner liner that will degrade and wreak havoc, with no warning.

If the line is not in an enclosed area, like on an inboard engine, just buy both connectors, a primer, and the right length of regular black fuel line from the parts store. The sun will degrade it in a couple years, but that's easier to fix than going through the whole fuel system when the other stuff fails.

Originally Posted by Atimm693

Those silver "marine" fuel lines are garbage. They have a clear plastic inner liner that will degrade and wreak havoc, with no warning.

If the line is not in an enclosed area, like on an inboard engine, just buy both connectors, a primer, and the right length of regular black fuel line from the parts store. The sun will degrade it in a couple years, but that's easier to fix than going through the whole fuel system when the other stuff fails.

Some friends warned me about this, they said "All grey marine fuel hoses are NOT the same, go with the Shields Silverado 4000, it's the real deal". True enough, you can look around and find grey fuel hoses that are cheap crap and will not hold up, nor does it have the Coast Guard approval numbers on it. The good stuff is Coast Guard approved, Type B1-15, Ethanol Resistant, Ultra Low Permeation that meets EPA and CARB standards, heavy duty reinforced inside and out, and comes with a two year warranty.
Lots of info on the hose is in the link posted above in my previous post. If you shop around online, the price is not too bad, either.