mercury 7.5hp fuel issue please help

Discussion in 'Outboards' started by runninlope, May 3, 2014.

  1. runninlope
    Joined: May 2014
    Posts: 4
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    Location: colorado

    runninlope New Member

    Hey guys/gals. I have an early 70's mercury 7.5hp 2 stroke outboard. Once I start it and take off it runs like a striped *** ape, but after about 10 seconds it starts sputtering and will die if I don't throttle down. I noticed that once it starts doing this I can squeeze the primer bulb and it isn't firm. I can squeeze gas into it and it picks back up again. It seems like my fuel pump isn't keeping up but I have rebuild the carb and pump and it hasn't changed anything. Please help boat season is among us!
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Try elevating the tank for a gravity feed test, if the problem still the same, it would suggest obstruction somewhere along the line.
     
  3. runninlope
    Joined: May 2014
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    Location: colorado

    runninlope New Member

    I tried that too but it still doesn't run any hotter than half throttle and I have all new fuel lines. I just have my line ran into a plastic jug would that be the problem ?
     
  4. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    Needle valve in carb not sticking ?
     
  5. whitepointer23

    whitepointer23 Previous Member

    have u tried another squeeze bulb. if the check valve in the bulb is leaking back you will have the problem u describe. how fast does a stripe assed ape go .
     
  6. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,389
    Likes: 1,023, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Maybe the bulb is only allowing fuel through under pressure. Whatever the case, should try another one.
     
  7. runninlope
    Joined: May 2014
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    Location: colorado

    runninlope New Member

    Idk how fast it goes hut it moves my little boat pretty quick. But I feel like the fuel pump is either really weak or I have an air leak somewhere.
     
  8. Westfield 11
    Joined: Apr 2008
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    Location: Los Angeles

    Westfield 11 Senior Member

    How does it run with the cap off of the gas tank? Clogged vent?
     

  9. runninlope
    Joined: May 2014
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: colorado

    runninlope New Member

    It runs the same, the fuel can is vented well. Does it need to be a boat fual can or can i just have my hose going into a 5 gallon jug?
     
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