Intake backfire

Discussion in 'Bubba's Outboards' started by troyedm, Mar 22, 2007.

  1. troyedm

    troyedm New Member

    Messages:
    83
    State:
    edmond oklahoma
    when at idle i have a occasional intake backfire. i really don't remember it doing this when i bought the boat and motor new. its a 90 hp 4 stroke 2000 year. it doesn't do it every revolution, about every 5 seconds, it will do a poof from the intake at idle. does ok at high speed. haven't had it on the lake, been running it in a tub of water. could this be normal? could it be the fuel, its been stabilized and is only a year old. could it be the ecm changing the ign timming at idle? a friend of mine says he remembers it doing it when it was new. plugs and wires are good. any thoughts?
     
  2. JAYNC

    JAYNC Active Member

    Messages:
    1,312
    State:
    Newport N.C.
    Some engines will do that if you are moving the throtte lever by the carbs and not the actual throttle lever on the remote control. Mine will do it when its cold sometimes when I am flushing it. Has a lot to do with no or little backpressure on the exhaust.
     

  3. troyedm

    troyedm New Member

    Messages:
    83
    State:
    edmond oklahoma
    thanks for the input. sounds right, as it had no load on it. (was in neutral) i just didn't want a lean condition to burn it up. never got a heat warning in the 15 minutes i ran it, so maybe I'm worrying for nothing.
     
  4. JAYNC

    JAYNC Active Member

    Messages:
    1,312
    State:
    Newport N.C.
    as long as the water stream from the tell tale is coming out with good force you have nothing to worry about. Mine will make a hole in the ground.
     
  5. Phil50

    Phil50 New Member

    Messages:
    42
    State:
    Il
    One can have good cooling water flow and still ruin a cylinder from a lean mixture, like a plugged main jet on one of the carbs.