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  1. #1
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    Jan 2012
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    2.5 280 hesitates off idle to wot.

    I have an 2003 JSRE Merc 280 SS, upon hard acceleration it hesitates/boggs for 2-3 seconds before it really picks up, other than the hesitation it runs great. Pulls hard all the way to the limiter. I need to check the tps but other than that any advice or other things to check would be appreciated.
    Thanks.

    Xb2003 - 300xs
    100+ mph club


  2. Mercury 3L/4 Stroke/Verado Moderator EuropeanAM's Avatar
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    #2
    Make sure the vacuum reference hose and fitting (for the MAP sensor) aren't plugged with congealed fuel....


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  3. Member
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    #3
    I did check the map, but I'll check it again thanks.

    Xb2003 - 300xs
    100+ mph club


  4. Member
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    Mar 2005
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    waynesville
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    267
    #4
    What prop u running?
    Allison XB 2002, 2.5 280

  5. Member
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    Jan 2012
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    Gulfport
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    #5
    24p et and 26p hydromotive ot 4

    Xb2003 - 300xs
    100+ mph club


  6. Member
    Join Date
    Nov 2010
    Location
    Humble,TX
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    4,377
    #6
    Either of those should fire out of the hole, so that's not the issue.

    Svs or factory horn front? If it's not the map reference plugged it could be the map itself.

    Some racers with svs front have used a manual mighty vac style pump to clear that up , but should t need it. Could be rich at idle and loading up.

    Try setting in down and trim down and immediately plane off again. If it bogs it's map vacuum related. If it doesn't it's the tune

  7. Member
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    Jan 2012
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    #7
    Horn, explain this mighty vac? When its on the hose I cant push the thottle blade open an 1/8" with my finger and it idles down and runs rough.

    Xb2003 - 300xs
    100+ mph club


  8. Member
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    Nov 2010
    Location
    Humble,TX
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    4,377
    #8
    Some slide fronts, Svs gold, smiling jacks etc don't pull enough vaccum at idle, motor thinks it's at a higher throttle position and goes full WOT fuel table so they are fat and bog out the hole. The vaccum pump pulls the vaccum on the map and a solinoid releases the vac on Wot.


    With a horn front you won't have that issue unless it's a modified big bore horn front.

    I'm thinking map, lines leaking or fuel curve is too fat at low speed.

  9. Member
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    #9
    Thanks

    Xb2003 - 300xs
    100+ mph club


  10. Member
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    Jan 2012
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    Gulfport
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    #10
    I believe it was a bad map sensor seems to be working now but have not put it in the water, thanks

    Xb2003 - 300xs
    100+ mph club