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    early 427 Chevy mercruiser base timing

    I need to know the exact base timing for these rebuilt 11:0 Chevy Mercruiser engines in my 74' Concord boat. Currently they are set at 10° btdc. I removed the Thunderbolt ignitions, and replaced them with DUI mechanical advance marine distributors. Thanks
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    1974 Mercruiser thunderbolt tach conversion

    GM marine grade from Marine Parts Source in Whitehouse, TN. GM marine grade from Marine Parts Source located in Whitehouse, TN. Thanks a bunch for the schematic my friend 😉
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    Tachometer conversion

    Thanks for the info...only the port engine tach is operational...the synch is located on the flybridge, and is disconnected...any additional info would by greatly appreciated 😉
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    Tachometer conversion

    I recently retrofitted my 74 mercruiser 427 engines with marine GM high energy ignition systems. I completely gutted the Thunderbolt ignitions. The port engine tach reads approx. double the actual rpms. I havent even connected the gray tach wire on either engine so where is this signal coming...
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    1974 Mercruiser thunderbolt tach conversion

    I retrofitted my 427 mercs with GM hei ignitions....port motor still shows approx. double rpm on tach...gray tach wire on hei isnt even connected...where is this seemingly spurious signal coming from ?
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