Mercruier ThunderBolt IV HEI Ignition System

Applications run from mid 80's thru mid 1990's

The thunderbolt IV ignition system designed by mercruiser is by far one of the most dependable systems to ever be on the market. Durable and simple to test it has stood the test of time with remarkable performance over the years.

Below is the test flow chart which requires only a volt meter. All tests should be done with a "KNOWN" good battery and test for voltage drop at the starter first, then the ignition coil, during cranking, before proceeding with these steps. (See minimum voltage page in directory)


tbolt-IV-trouble.gif (27825 bytes)


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