Ignition system eating wires/coils.

nikon

Petty Officer 2nd Class
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Jan 12, 2011
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193
93' 350 Mag alpha one gen 2, thunderbolt IV I believe.

Started 2 years ago, thought I kept blowing coils on new wires. I'd replace the coil and it would fire right up. Happened again last season, this time I tried changing just the coil wire and it fired right up. Fast forward to last weekend, half way home she died on me. Still had the 'bad' coil wire I had removed last season in the boat, so while sea-tow was on their way I decided to try it. Low and behold it started right up, it felt down on power while planing but it made it home.

What the heck is going on? I'm running the proper quicksilver coil as my seloc manual explains its some special kind of coil and running quicksilver wires as well. Engine has about 460 hours on it, before all these problems in the first ~5 years of ownership I never had to replace anything on the ignition system, but did as typical maintenance. What am I doing wrong here? Or what part has gone bad in the boat? I'm ready to completely ditch the thunderbolt system and get a mallory if this keeps happening. Cap, rotor, coil and all wires were replaced last season. Going to get new plugs/wires for it and install tomorrow, I assume this will fix the problem temporarily.

Any help/insight appreciated.

If I do need to replace the whole system, is this the right one?
http://bpi.ebasicpower.com/pc/MAL9-26000/MER10A-IB
 

nikon

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193
Re: Ignition system eating wires/coils.

Well, I didn't feel like waiting and dealing with the thunderbolt anymore. Mallory is on order. Do I need anything else? Resistor or anything? Or is that built in?
 

Bt Doctur

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19,093
Re: Ignition system eating wires/coils.

without knowing why you losing coils ,the question cant be answered.whats the voltage at the + side of the coil?
 

nikon

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Re: Ignition system eating wires/coils.

12 volts with the key in the run position...been through the seloc manual and the mercruiser manual to troubleshoot, nothing wrong per the manuals.
 

Mischief Managed

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1,928
Re: Ignition system eating wires/coils.

12 volts with the key in the run position...been through the seloc manual and the mercruiser manual to troubleshoot, nothing wrong per the manuals.

That sounds too high. should be around 9 volts, if memory serves. I suspect you have a fault in your ballast resistor circuit. Would explain the failing coils and wires.
 

Don S

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Re: Ignition system eating wires/coils.

That sounds too high. should be around 9 volts, if memory serves. I suspect you have a fault in your ballast resistor circuit. Would explain the failing coils and wires.

The voltage sounds fine, he doesn't have points nor does it have a resistor wire or ballast resistor in it. He should see battery voltage at the coil.
 

nikon

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Re: Ignition system eating wires/coils.

Does the Mallory operate at 12v also or do i need a resistor?
 

Chef Shawn

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Jul 15, 2012
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Re: Ignition system eating wires/coils.

Seloc manuals are crizzap. I know, I bought one. Anyhoo, look for alternator back-feed to the coil. It happened to me, boiled my coil after a couple of hours, gives all charging volts to coil, even when they aren't needed: should be an in-line diode that can be replaced. Check purple wire off alternator.
 

nikon

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Re: Ignition system eating wires/coils.

Its a new single wire alternator. Bearing were going bad in the old one...voltage is correct when running and key in run position.
 

Chef Shawn

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Re: Ignition system eating wires/coils.

OK then,

Did you buy the new alternator in hopes of solving the old problem? IE: With the old alternator did you have the same problem?

The coil gets power from the battery upon cranking (starting) and then lives off of the alt. juice while the boat is running. I hate to sound like a broken record but a bad ground will make ALOT of problems.
 

nikon

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Re: Ignition system eating wires/coils.

Problems existed with the old alternator as well. Old alternator had a ground post, new alternator doesn't so I left it loose (it was just running to the block anyways), just assumed being bolted to the engine was a good enough ground. What other grounds can I check?
 

Don S

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Re: Ignition system eating wires/coils.

Disconnect the tach and see if that cures the problem.
 

nikon

Petty Officer 2nd Class
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Jan 12, 2011
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193
Re: Ignition system eating wires/coils.

All instruments were replaced last year, but I will try it. I assume you mean pull the lead off the coil. Only other thing I can think of is the hour meter runs hooks directly to the coil (from the factory) could this be a cause?
 

Don S

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Re: Ignition system eating wires/coils.

Your coil should have two gray wires on the negative terminal. Disconnect the one going to the tach, not the distributor.
 
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