Merc 496 loud smacking noise. Won’t start.

Discussion in 'Sport Cruisers' started by McFly, Jun 14, 2019.

  1. McFly

    McFly New Member

    9
    May 10, 2019
    MN
    2006 280DA
    Merc 496/Bravo III
    Hi guys, hoping someone could give me some insight. I purchased a 2006 280 with the single 496...360hrs. Boat tested great where purchased. Tried to start it yesterday and the starter engaged but wouldn’t turn over and made a loud smacking noise. Tried one more time and the same. Starter now just spins. Oil is clean, batteries are new. I’m just sick that I might have a major and expensive problem. Freshwater boat. Any advice would be greatly appreciated.
     
  2. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS
    Can you put a breaker bar on the crank bolt and see if it spins easily?
     
  3. Bt Doctur

    Bt Doctur Well-Known Member

    Aug 21, 2010
    New Jersey
    Ex SRV 240 Weekender twin
    in between
    It sure will spin freely once you break that bolt,
    Worst advice ever.

    Remove all the spark plugs, then try the starter again. If the starter just spins and not the motor you could have destroyed the bendix drive from a hydro-lock or at worst bent or broken a connecting rod.
    If your on land ,remove the drive and insert a T bar with a old shaft welded to it
    or remove the crank bolt, remove the 3 pully bolts, remove pully and reinstall the 3 bolts and use a bar between them to turn the motor
    If water comes out a spark plug hole ,its a hydro-lock and you need to find out where the water came in from. The usuall suspects are corroded elbows or corroded/cracked manifolds
     
    Last edited: Jun 14, 2019
  4. Espos4

    Espos4 Well-Known Member

    Jan 1, 2017
    Long Island NY
    2007 240 Sundeck
    350 MAG Bravo 3 W/DTS

    Did you miss where I said “easily”??
     
    techmitch likes this.

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