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  1. J

    4.3 Mercruiser Spark knocking at high rpm

    After reading other posts and forums I am also realizing that I am reving to high when WOT the tach on the dash is showing right at 6000 rpm I am curious if with the engine over reving like this, if this could be the root cause. And curious why it’s not limited out at 4800 like I’m reading. I...
  2. J

    4.3 Mercruiser Spark knocking at high rpm

    Hello, I am new to forum and have had my boat three years. It is a 1997 VIP Valiant with a 4.3lx gen+ thunderbolt 4 ignition. My boat as had the same issue the last year of when it get to operating temp 160-180 and under load it will start spark knocking at full throttle. You can back out of...
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