150 yamaha surging

Discussion in 'Outboard Maintenance' started by jeff_erickson, Jul 18, 2011.

  1. Jul 18, 2011 #1
    jeff_erickson

    jeff_erickson I Love microskiff.com!

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    I have a 150 hp yamaha v max carbed and it surges @ high speed bad, it also now starts like a efi with no choking necessary. I see alot of gas film on the water. I did a compression test with 110 across the board. A a fuel pump pressure of 4.5 lbs on both.
     
    jeff_erickson, Jul 18, 2011
    jeff_erickson, Jul 18, 2011
  3. Jul 18, 2011 #2
    Brett

    Brett > PRO STAFF <

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    Fuel feed would be my first guess.
    Checked your plugs to see if you're running rich?
     
    Brett, Jul 18, 2011
    Brett, Jul 18, 2011

  5. Jul 19, 2011 #3
    twitch

    twitch Well-Known Member

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    I'd check the fuel pumps again. Unbolt them from the block and pump the primer, if any fuel comes out of the engine side of the pump the diaphragms are shot. A bad FP diaphragm can make you run rich at idle and lean on the top end, just as you described. [smiley=2cents.gif]
     
    twitch, Jul 19, 2011
    twitch, Jul 19, 2011
  6. Jul 19, 2011 #4
    jeff_erickson

    jeff_erickson I Love microskiff.com!

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    Thanks, I think I will rebuild both pumps to be on the safe side. Cheap fix for a 2005 engine
     
    jeff_erickson, Jul 19, 2011
    jeff_erickson, Jul 19, 2011
  7. Jul 19, 2011 #5
    jeff_erickson

    jeff_erickson I Love microskiff.com!

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    Do you think ethanol might have caused the trouble?
     
    jeff_erickson, Jul 19, 2011
    jeff_erickson, Jul 19, 2011
  8. Jul 19, 2011 #6
    DuckNut

    DuckNut Brandon, FL

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    Ethanol is not the root of all engine problems. Most likely it is the years of use that simply deteriorated the seals and gaskets.
     
    DuckNut, Jul 19, 2011
    DuckNut, Jul 19, 2011
  9. Jul 19, 2011 #7
    twitch

    twitch Well-Known Member

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    If you are running ethanol I'm sure it contributed, if in fact your fuel pumps were the source of your problems. ETOH is hard on rubber parts.
     
    twitch, Jul 19, 2011
    twitch, Jul 19, 2011
  10. Jul 19, 2011 #8
    cutrunner

    cutrunner Cert. Yamaha technician

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    Ok. If your fuel pump diaphrams are white, they are mylar and most likely your problem, the updated ones are black and made of neoprene. Or.. Another syptom of your problems is a stuck float or a "sink" (a float with a hole in it that doesnt, well float lol)
     
    cutrunner, Jul 19, 2011
    cutrunner, Jul 19, 2011
  11. Jul 22, 2011 #9
    jeff_erickson

    jeff_erickson I Love microskiff.com!

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    I replaced both fuel pumps and it runs like new! Thanks
     
    jeff_erickson, Jul 22, 2011
    jeff_erickson, Jul 22, 2011
  12. Jul 22, 2011 #10
    twitch

    twitch Well-Known Member

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    Glad ya got it fixed.
     
    twitch, Jul 22, 2011
    twitch, Jul 22, 2011
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