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

  1. #1
    Join Date
    Apr 2018
    Posts
    4

    Default Blaster 2 coil problem, can the old 6420 6AL box cause this?

    OK so I'm new here and this is my first post on MSD ever, so please bear with me as I'm a noob to this MSD stuff. I have a 28 foot 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 engine 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 engine. The engine 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 three components were installed together.

    So now that you have the background I'm 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!
    Attached Images Attached Images

  2. #2

    Default

    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
    Join Date
    Apr 2018
    Posts
    4

    Default

    Thanks for the reply! I'll get an 8222 and keep the other as a backup.

  4. #4
    Join Date
    Apr 2018
    Posts
    4

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    So I purchased the HVC and tested the resistance on it out of the box. 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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    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
    Posts
    4

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    I just used two different meters, both of which zeroed out when touching the leads together. Both registered around 6040 & 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 it's brand new? Attached is a pic of the serial number on the bottom of it.
    Attached Images Attached Images

  7. #7

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    Just yesterday I posted “Blaster 2 8222 Resistance” I had the same problem. I bought one it bench tested 6.275K secondary out of the box. I brought it back, the store took another one off the shelf, I tested it and got same reading. Could you please tell me the final disposition of your issue I’d like to return it, as I don’t trust it.

  8. #8

    Default

    It's supposed to be 4,500.
    So it's ether missing some wire length, OR, a larger gauge wire is being used. Are you sure that what you bought is a real MSD coil?

  9. #9

    Default

    I bought it in a reliable speed shop I’m sure it’s the real deal, not their fault. The problem is “Made in China”
    Last edited by 312YBlock; 09-11-2021 at 06:39 AM.

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