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MSD Marine box wiring

Old 09-21-2021, 06:36 PM
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Default MSD Marine box wiring

Hello All,
The MSD wiring diagram shows to use the red wire to turn off the unit. My Mecruiser used the purple wire that runs to the coil to shut things down along with the kill switch. I have been trying to reach MSD but no luck. What is the save way to wire the MSD unit, if I use the red wire I need to remove the purple coil and tach wires some help needed. Thanks Jeff
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Old 09-21-2021, 09:39 PM
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Which box are you running?
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Old 09-22-2021, 04:51 AM
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MSD 85701 Dist and 6425 6AL Box.
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Old 09-22-2021, 06:10 AM
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Connect the thin red wire from the MSD unit to the purple ignition power wire from the harness.

Important - The only connections at the coil should come from the MSD box. Do not connect the gray harness tach wire to the coil. See diagram below.


Last edited by TomZ; 09-22-2021 at 06:58 AM.
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Old 09-22-2021, 07:01 AM
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One last note... I'd keep an extra distributor pickup on the boat. A spare box couldn't hurt too. They aren't the most reliable of ignition systems.
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Old 09-22-2021, 06:17 PM
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[QUOTE=TomZ;4806588]One last note... I'd keep an extra distributor pickup on the boat. A spare box couldn't hurt too. They aren't the most reliable of ignition systems.[/QUOI have a thunderbolt four now and have several plugs that read different. Im not 100 % sure its a ignition problem but leaning that way what ignition system would you recommend?
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Old 09-22-2021, 06:21 PM
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I can say this the technical dept at Holley is useless three days over 2 ours on hold and they are unable to answer the simplest questions. I basically new more than this guy.
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Old 09-22-2021, 07:01 PM
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The TBIV is pretty reliable… more so than the MSD. What’s up with your plugs?
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Old 09-22-2021, 07:01 PM
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Originally Posted by Zinger View Post
I can say this the technical dept at Holley is useless three days over 2 ours on hold and they are unable to answer the simplest questions. I basically new more than this guy.
I come here for technical support.
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