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    Anybody have past experiences with a bad amplifier?

    With the purple wire connected to the + side of the coil, I get 12.5v and starts. Other times and intermittent, It shows 10.8v at + side of coil (no start). Remove the amplifier (purple) wire from the + side, back to 12.6v, touch the amp wire back to the + side, drops to 10.8v and can hear a...
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    Help with Ignition Coils

    Mercruiser Thunderbolt IV ignition system. I have two coils and could they both be bad even though new? they are different manufacturers. Ohm checking the secondary windings, both read around 9.5 on the 20k setting, but on the primary windings at 200, one reads 0.7 at the center post and the...
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    Voltage Drop

    Bought a used 1987 boat with a mercruiser 230 GM 5.0L V-8 that has the Thunderbolt IV ignition System. Traced down some ignition parts that were faulty and got it running. Question I have, if any of you know about the Thunderbolt ignition systems, is I get between 12.2 and 12.5 volts everywhere...
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    Ignition Module Bad

    Mercruiser Thunderbolt IV ignition system. Sometimes almost 13v on + side of the coil, sometimes 10.5v at the + side of the coil. When at 10.5v, no start. When at almost 13v, fires right up. New cap, rotor, coil, key switch and kill switch. If I take the purple wire off the + post that runs to...
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    Engine Serial Number

    Google search shows where to locate a serial number tag on my Mercruiser, but I have looked all over the engine and cannot find the serial number tag. Mercruiser 230 V-8 w/Thunderbolt IV. Block bell housing says GM Any other tips for finding the serial number of the engine?
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    Coil Voltage Problem

    I am at a loss. Bought a 1987 Chaparral 20" with a GM Mercruiser 230 Alpha One Thunderbolt Ignition as a project boat. It now runs great, when it starts after working on it. The problem I am having is when it will not start, the + side of the coil reads about 8v and about 4v on the - side. When...
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    Temperature Reading (Scratching my head)

    Cleaned and tested the temperature needle gauge on the dash, works fine. Temp Sensor on block was bad. Replaced it with a new sensor. Applied teflon tape to the threads, connected the sending wire and turned on the ignition switch. The temperature gauge immediately reads around 150* with a cold...
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    Need HELP!

    I bought a 1987 Chaparral 20' boat with the Mercruiser 230, V8, 5.0L Thunderbolt IV ignition system. I am at my wits end chasing a starting issue. Put on a new carburetor, ignition coil, cap, rotor, and spark plug wires. Sometimes it starts, sometimes it doesn't. Been checking the voltage at the...
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