How does the fuel supply work on a typical outboard

Discussion in 'Powerboats' started by wet-foot, Jul 29, 2007.

  1. wet-foot
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    wet-foot Senior Member

    Typical hose with prime bulb has 2 connectors. One is obviously the fuel supply. Is the second one a fuel return line to the tank or a air vent?
     
  2. Guest625101138

    Guest625101138 Previous Member

    I cannot comment on all systems but you are probably refering to the OMC connector. It has a fuel nozzle and a connecter retaining pin that mates to the clip on the hose fitting. There is also a valve in the tank connection head, activated by small stainless pins when the the fuel line is in place, that opens the fuel nozzle.

    Some tanks have a small threaded vent in the fuel cap to allow the tank to breathe. This must be loosened. It is best to loosen the vent before connecting the hose because the tank can be under pressure and can flood the engine in hot weather. If the vent is not released in operation, the tank will go into vacuum and starve the engine. The OMC female fitting on the hose have a sealing ball at both ends to prevent fuel leakage when disconnected.

    I have not seen a fuel line with a fuel return hose on any outboard.

    Rick W.
     
  3. razbarb
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    razbarb Junior Member

    The second connector is just that, a connector.
    It allows for a tighter and stronger connection for the fuel hose.
    I learned the hard way about the vent on the fuel tank!!
    Gee rowing is good exercise.
     
  4. charmc
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    charmc Senior Member

    Partly right, Tim. Fuel return lines are for engines that use fuel injection. For a long time diesels were the only marine engines with fuel injection. The newer outboards with EFI have return lines.
     
  5. timgoz
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    timgoz Senior Member

    Always a good day when you learn something, eh Charlie? You noticed I qualified it with "as far as I know". :)

    Tim
     
  6. wet-foot
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    wet-foot Senior Member

    I guess a second tank with a separate fuel line would be out of the question. The tank actually has 4 line coming from it; 1. is fuel - 2. is reserve - 3. is fuel return - 4. is a one way air vent that allows air into the tank to replace the displaced fuel. I guess the only thing to do is enlarge the tank and move the fitting cluster to the top of the new tank. Or just be satisfied with refilling the tank when it runs low! Thanks for clearing up the fuel line issue for OB's, thought there where 2 connections ....... didn't realize the second was just a pin. I can't use a vented tank because when I flip my boat fuel will leak out causing harm to the environment. "Would not want big Al on my case" :p
     
  7. timgoz
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    timgoz Senior Member

    "Flip my boat". Whats up with that Wetfoot? Is it stored that way with tank in, or are you having a bad premonition? :(

    Hope its the former. Can't you remove the tank if thats the case? Any boat physically small enough to flip would have a removable tank most times.

    Sorry for all the ?'s but your statement has me intrigued.

    Have a good one.

    Tim
     
  8. charmc
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    charmc Senior Member

    Tim, you took the words right off my keyboard.

    Wet-foot, I have visions of you being a stunt boat driver. :)
     
  9. wet-foot
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    wet-foot Senior Member

    No big deal! I built a 11' jet drive inflatable that runs in real shallow water but is mainly for use in big waves. So yes, if it gets rolled over by a big wave you can basically leave it upside down with no fuel leakage plus the engine and all electrical remain dry. Flip it back over and away you go. The boat only has a 20 liter tank which I would like to increase in size, that's the reason for the original question.
     
  10. timgoz
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    timgoz Senior Member

    Wetfoot,

    Sounds like a real fun boat. Used to guide whitewater up to Class 5. Love "negotiating" big waves & such under the right circumstances.

    Have fun in the summer sun!

    Tim
     
  11. razbarb
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    razbarb Junior Member

    I just read all of the replies and realise how basic my reply is.
    I assumed the majority of outboards would be carburetted still.
    Sounds like your boat would be huge fun.
     

  12. wet-foot
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    wet-foot Senior Member

    The boat is small but I tow it with a Toyota Yaris. Got rid of the 4x4 and when you figure in my fuel savings it really is like getting a free boat. My annual fuel costs for the car and boat are less than they were for just the truck. I enjoy traveling to different lakes and the ocean is a go also. Not only do I feel extra safe with the inflatable but clean up is so fast and easy.
     
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