Petronix coil installation on older Mercruiser

tfisher1975

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Aug 27, 2015
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Hello everyone, I know that this is an older thread, and I am new to this forum, but I was wondering if I could get just a bit more guidance. As luck would have it, I also have a 1967 Reinell with a 120 HP Mercruiser, so this thread is perfect! I just put a Pertronix electronic ignition in place and all went well on that front. When I bought the Pertronix module, I also purchased a Pertronix coil, to replace my aging original. The coil that was recommended to me was the Flamethrower 40,000 with 3 ohm built in resistance. Now I'm realizing that in order to keep this coil, I need to bypass the boat's ballast resistor circuit so that I don't have too much resistance stacked up. I was thinking of running a wire directly from the hot side (where the 2 white wires come in...see photos on above posts) of the ballast resistor to the + coil connection and taping up the old + wire (white) that came from the output side of the ballast resistor to the coil. The Pertronix coil installation instructions recommend removing the resistor, but there is still one wire (tan) that comes out of the ballast resistor that attaches to down on the starter. I don't want to monkey around too much with things I know little about. I'm wondering if I should just ditch the Pertronix coil and get a standard automotive coil without resistance. Any thoughts?

Thanks!
 

aspeck

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May 29, 2003
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18,588
http://forums.iboats.com/forum/engi...es/567388-ballast-resistor-and-coil-confusion

Here is the older thread you referred in your post. I moved your post to a new thread to avoid confusion and help you stay within the rules of the forum. Good luck with your issue. I cannot help you, it is not my area of expertise.

Oh, and welcome to the forum! You will find a lot of knowledgeable people here. It is a great place to hang out!
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Couple of ways to go about it. Just put the wire you have in mind in place, and leave the existing ones also there. It'll not effect anything.

Or you could add your new wire in, and remove the wire from the starter to the coil all together (the reason it's there is to supply full voltage to the coil while cranking the engine. As you have a full voltage wire in place all the time, this wire becomes redundant.).... Tape up or leave in place the existing resistance wire (having it still wired up won't drop the voltage to the coil)....

Chris.....
 
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tfisher1975

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Aug 27, 2015
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2
Thanks for the advice Chris. I did as you suggested and patched a new wire from the input side of the ballast resistor to the (+) side of the coil. I also reattached the existing wiring as you said that it would not result in any voltage drop to the coil. I started it up and it ran nicely! Is there anything else I should check voltage wise while it's running before I take it out and run it? Thanks for your advice Chris, and thanks to all who gave input on this subject previously...what a great resource!
Todd
 
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Mar 27, 2010
Messages
3,008
Thanks for the advice Chris. I did as you suggested and patched a new wire from the input side of the ballast resistor to the (+) side of the coil. I also reattached the existing wiring as you said that it would not result in any voltage drop to the coil. I started it up and it ran nicely! Is there anything else I should check voltage wise while it's running before I take it out and run it? Thanks for your advice Chris, and thanks to all who gave input on this subject previously...what a great resource!
Todd

Your only scratching the surface here... :thumb:
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
... Is there anything else I should check voltage wise while it's running before I take it out and run it? ...

If you have a good digital multimeter, just check your alternator is doing the right thing and charging at between 13.8v and 14.5v.

Other than that, nope.... Have fun.... :)

Chris.......
 
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