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Thread: Blaster 2 coil problem..can the old 6420 6AL box cause this?

  1. #1
    Join Date
    Apr 2018
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    Default Blaster 2 coil problem..can the old 6420 6AL box cause this?

    Ok so I am new here and this is my first post on MSD ever so please bear with me as I am a noob to this MSD stuff. I have a 28ft Magic Deckboat that has a customer built BBC 565 with MSD 6AL (6420) ignition box, Blaster 2 coil, #85551 MSD distributor cap and Street Fire Wires. The motor makes about 640 HP. I was running the boat fairly hard a couple weeks ago at Lake Havasu and it died on me. Immediately I was worried I blew the custom motor. The motor cranked over and almost re-started but it never did. I thought it was a fuel issue. Starting fluid did not get it going so we figured a spark issue.

    I took the boat to my marine tech and we found no spark to the spark plugs, we tried trougleshooting the ignition box and no spark to the main wire to the distributor cap, we replaced the Blaster 2 with another Blaster 2 and WHA LA! The boat started right up and ran like a champ...WAYYY better than I had heard it run in awhile. I had noticed a couple times on the water that it seemed the boat kind of "jumped" forward real quick and then back...And I've also noticed it all of a sudden backoff even though I had the throttle pinned...I thought nothing of it but maybe it was early signs of the coil going out??? Attached is a pic of the MSD setup. I have no clue how old all this stuff is as I bought the boat used and it is about 12 years old. The serial # on the 6420 is 743535 if that might tell its age at all, and assuming these 3 components were installed together.

    So now that you have the background I am wondering if the coil went bad because the 6420 box is jacking the coil up?
    Is it normal for the coil to go bad?
    Should I now carry a spare coil?
    Should I do something to test to make sure the 6420 box isn't putting out anything funky that would jack up my new Blaster 2?

    Thanks to anyone who might have input on this issue and concern!
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  2. #2
    Join Date
    Jan 2018
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    I wouldn't suspect the MSD Box causing an issue with the coil. But I would recommend put an 8222 high vibration coil on it since the blaster 2 coils are oil filled and with it being on a boat the vibrations it receives could cause issues. Also, once and MSD box goes out they just quit working since it pops something on the circuit board making it not operate anymore.

  3. #3
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    Apr 2018
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    Thanks for the reply! I will get an 8222 and keep the other as a backup.

  4. #4
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    Apr 2018
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    Quote Originally Posted by Nofears67 View Post
    Thanks for the reply! I will get an 8222 and keep the other as a backup.
    So I purchased the HVC and tested the resistance on it out of the box and the primary was 0.7 ohms and the secondary was 6,040 ohms...isn't the secondary a little high?

  5. #5
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    Jan 2018
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    If you put the leads of your meter together what resistance reading do you get? We normally want the readings to be around 20% of the number we recommend. So, that coil is still reading high as we would recommend the max being around 5400.

  6. #6
    Join Date
    Apr 2018
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    I just used 2 different meters, both of which zero'd out when touching the leads together. Both registered around 6040 and 6050 ohms on the secondary. The primary seems right around 0.6 to 0.7 ohms. Do I need to return it for warranty replacement even though its brand new? Attached is a pic of the serial # on the bottom of it.
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