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Recent content by JohnGinsberg

  1. J

    need help diagnosing Mercruiser 7.4 with Thunderbolt IV ignition

    Need help. My starboard engine is a 1988 Mercruiser 7.4 (=a chevy 454) with a Thunderbolt IV ignition system. Last time it ran well was last October 31. On that voyage, it started running rough. We have done a lot of work on it (see below) and it starts very well, but the engine will not rev...
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