Aluminum Fuel lines

Discussion in 'Boat Design' started by Katoh, Apr 19, 2011.

  1. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Good Evening
    I am slowly rebuilding a 20Ft Aluminum boat with a diesel inboard. I have rebuilt the fuel tank and am going to replace all the fuel lines. The original lines are what seem to be crimped hydraulic hoses with threaded fittings, that lead to a fixed filter and junction clamp in the Engine well. They have not taken kindly to the salt water and fittings even the hose reinforcement is rusted. I prefer not to travel the same path.
    I was thinking of using aluminum fuel line with aluminum flared fittings from the tank to the filter and junction, then just rubber hoses to the motor. I have been told not to use Aluminum fuel line as vibration causes it to crack, is this so?
    If so what else would you recommended, copper would be good but not sure about dissimilar metal and corrosion. The tank sits in its own sealed well with a sealed aluminum floor above not the sort of thing you have easy access too, its a big job just getting to it, so I want this to last.
    Katoh
     
  2. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Aluminum lines will have corrosion and other possible problems with vibration too. The easiest is to use a marine fuel rubber hose from the tank to the engine.
     
  3. Lurvio
    Joined: Jul 2009
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    Lurvio Mad scientist

    Fasten the copper lines with rubber cushion clamps and use a rubber bushings going through walls. Should handle the issue of corrosion.

    [​IMG]

    Just a though.
    Lurvio
     
  4. CDK
    Joined: Aug 2007
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    CDK retired engineer

    Soft copper is the usual way to do that. Use neoprene lined clamps to prevent electrical contact with the aluminum; dissimilar metals can coexist as long as direct contact is avoided.

    Of course you can also use aluminum fuel lines, even all the way to the engine if you provide enough length by means of one or two loops between the last clamp and the engine. A/C and fridge compressors are connected that way.
    But the thin walled aluminum is prone to corrosion, so you need to protect it thoroughly with chlorinated rubber paint.
     
  5. Katoh
    Joined: May 2010
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    Katoh Senior Member

    I like the sounds of using copper and insulating it, one question what happens at either end, The first were it comes into contact with the aluminum tank, at the fitting the other were it joins the ally top of the diesel filter. The return will have a barb and and rubber hose no problem there.
    When I look further into it its probably better to use quality hose, stainless barbs and two clamps per barb, that way the return will be one continuous line and the feed will only have one joint.
    Can you use duralac on the fuel line fittings? or are you better off to use locktite thread sealer paste?
    Thanks
    Does anyone know were you can get Coal Tar Epoxy from in Australia, I want to paint my tank and fuel well in it.
     
  6. whitepointer23

    whitepointer23 Previous Member

    rubber fuel hose is the only way to go , you can route anywhere and it's so easy to do, i would never use metal fuel lines for that job. go to bunnings or miter 10, they stock coal tar paint .
     
  7. Taurus66
    Joined: Apr 2011
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    Taurus66 HRC Sourcing

    I am a hose builder of some years , may i be so bold to suggest that if you want something to last spend some money and make it the best.. Fuel is the last thing you need in a boat hull.. Make it stainless tube and you will thank me for it. If you need tube let me know.. Kind regards
     
  8. whitepointer23

    whitepointer23 Previous Member

    i am a boat owner of some years and i have never had trouble with fuel hose.
     
  9. Taurus66
    Joined: Apr 2011
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    Taurus66 HRC Sourcing

    I am not saying anything is wrong with fuel hose either, but in realistic terms stainless tube you are not likely to replace in a very long time.. provided it is secured as all things should be in a boat of any design.
     
  10. viking north
    Joined: Dec 2010
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    viking north VINLAND

    Two possible problems with rubber hose #1- if you are insuring your boat check with your insurance company for approval- they will most likely ask for a marine survey and there in might be a problem--subject to being easily cut by cargo or subject to burning off from a small fire and feeding that fire with a most combustable fuel creating a much bigger fire. The other problem is there has been alot of problems with so called fuel rated hose failing on generators manufactured in China. How saturated the world market is with this hose is anybody guess so if you do decide to go with hose, buyer beware. This house builder/boatbuilder agrees with the above housebuilder:Stainless is the way to go but allow a built in flex circle at your tank connection since this is hidden. The flex circle is nothing more than forming the line into a 360 small circle just before the connection. Look at the brake line connections to your autos master cylinder and you'll know what i mean. The connection to your engine should be made with a transition to a short piece fuel hose Flare your line and double hose clamp on all connections . To secure your line in place Clamp well and clamp often along a route that is not subject to being damaged. See Lurvios post above for clamp style in stainless or use heavy plastic of the same style. Another option you might look into is plastic fuel line, Ford is using it on their diesel trucks--Good luck Geo.
     
  11. Dean Smith

    Dean Smith Previous Member

    you are dead right, I have built many aluminum boats all sizes, I use ss on hydraulics, fuel
    On bigger supply I use flares, DUFFIELD on small like yours 5/16 you can use swage
    SS is very cheap compared with high grade synthetics but with sort runs like yours why not use synthetic fire resistant
     
  12. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Gentlemen
    Lots of good advise thanks for that.
    I did think about stainless but 2 matters come to mind. Firstly its far more brittle than aluminum, wouldn't it be worse in terms of vibration and cracking.
    secondly trying to work 1/2" or 3/8" tube is a pretty big ask, you couldn't use hand benders like for copper or aluminum, even putting a flare on it would need some special equipment.
    One thing that got me thinking was for the hydraulics hoses, from pump to trim cylinders s/s would be perfect. Again if you can work it?
    Wouldn't you still have the dissimilar metal problem even with stainless?
    katoh
     
  13. Dean Smith

    Dean Smith Previous Member

    I just said I had used it on all my builds, with no problems
    Also yes it is easy with hand benders, bends very tightly use either 1.2 or 1.6 wall. and in in annealed form bends easily with HAND former at 5/8 buy your tool at any good ac shop or plumbers merchants. brittle, ? try working it make and forwards til your hands are on fire 3/8 bends abt 30R
     
  14. whitepointer23

    whitepointer23 Previous Member

    point taken, something i have been thinking of is to run my fuel hoses inside a larger diam hose for the whole length what do you think of that idea, it would be well protected from chafing . like running wires through conduit.
     

  15. Katoh
    Joined: May 2010
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    Katoh Senior Member

    Dean
    Can you get tubing already annealed or do you anneal it yourself? I have some 1/2" OD .06" (1.5mm) wall 316 (I think 316 magnet wont stick to it) tubing enough to do the job, but there's no way I can bend it or flare it. My benders will snap in two, this I know I tried to bend some before.
    I haven't tried annealing it, maybe because I'm not sure exactly how to. But its solid and hard.
     
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