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Mercruiser 350 Mag MPI Backfire/POP

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    Mercruiser 350 Mag MPI Backfire/POP

    Hey all,

    Took the boat out this memorial weekend, ran great for 3 days wakeboarding/surfing. Last day I was wakeboarding, and my buddy (a seasoned boat driver) stuffed by bow through a wake it happens wasn't that much water maybe 20 gallons. I hop back in the boat and go to run it home, get to about 2500-3000 RPM right before plain and it back fired/popped, I was real quick on getting the throttle back to idle and it idled fine. Tried again, same thing, I limped it back at about 10 mph no issues I was not able to determine if it was an exhaust pop or an intake pop just That the pop was definitely an air pop and not a mechanical bang. Had blackwidow (Jack and Cheryl) look at, couldn't notice anything other than my starboard exhaust riser was a little warmer then the port. Ran it at idle to 3000+ Rpm no issues while in neutral. I reached for my tools and noticed my negative terminal on battery 1 was very loose, and the positive connection on battery 2 almost completely came off. I tightened everything down, and we went out and tested it, no issues ran great. (However I was empty on ballast and just 3 people in the boat). Could the loose terminals cause a reset in the ECM/throttle position sensor/IAC valve? I am still not convinced and neither was anyone else that that batteries could cause this. Also ran the boat 6 miles loaded down going home the next day no issues any help would be great.
    My life's journey is not ending up looking pretty, its sliding in broadside, used up, worn out, screaming "What a Ride"

    #2
    Certainly possible that a battery disconnect wil cause the ecu to have a fit. The alternator voltage would be all over the place.

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      #3
      I didn't think to look at the voltage when it happened so I cant confirm if it was jumping around or not.
      My life's journey is not ending up looking pretty, its sliding in broadside, used up, worn out, screaming "What a Ride"

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        #4
        that very well could be it you lose power from the battery it can cause all kinds of things to go screwy injuectors not firing right plugs not firing right tps shuts down tons of things shut down or do not function correctly when the battery disconects it could have also caused the battery to not charge correct and have low voltage and it requires more power to run the engine at a higher rpm so low voltage coming from the battery could have also caused it i would think you found your problem. im sure your like me and would still be worried but take it out on a few short trips and if theres no problem then i wouldnt worry about it to much.

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          #5
          Thanks for the input guys, as it turns out I just purchased a 2006 Tige 24Ve and the old Centurion is going away. it was a great boat and that was the only problem I ever had with it, seems like I got it fixed. Thanks again, just one more thing to check before heading out.
          My life's journey is not ending up looking pretty, its sliding in broadside, used up, worn out, screaming "What a Ride"

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            #6
            thats awesome man congrats on the new boat!!!

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              #7
              Originally posted by Thegerman618 View Post
              Thanks for the input guys, as it turns out I just purchased a 2006 Tige 24Ve and the old Centurion is going away. it was a great boat and that was the only problem I ever had with it, seems like I got it fixed. Thanks again, just one more thing to check before heading out.
              Going to the dark side eh??

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                #8
                Yea, Finally made it over here seems like you guys are having way more fun then the other guys LOL
                My life's journey is not ending up looking pretty, its sliding in broadside, used up, worn out, screaming "What a Ride"

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