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Old 04-19-2011, 12:00 PM
Possum Possum is offline
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engine stops

My engine has taken to stopping suddenly as if it is out of gas. The longer I leave it off before restarting the longer it will run before stopping again. The engine is not hot, the gas is fresh and the tank is not vapor locking. Any suggestions?
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Old 04-19-2011, 12:12 PM
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Baltimore Sailor Baltimore Sailor is offline
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Sounds like a classic case of coil overheating. Does the engine quit suddenly, like you turned off the ignition, or does it slowly rumble to a stop?

The fact that the longer you let it sit after it fails (letting the coil cool down), the longer it will run before failing again, also points in that direction.

If your coil is more than a few years old, it wouldn't be a bad idea to spring for a new one. That way you both upgrade an important piece of equipment and, at the least, eliminate one possible cause of your problem -- if it doesn't fix it outright.

Good luck, and keep us posted.
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Old 04-19-2011, 01:37 PM
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Smile Coil likely

I agree with Baltimore Sailor...sure sounds like the coil needs replacing. Sometimes the condenser causes intermittent ignition failure also if you are using points and condenser.

Usually, if a fuel problem, it will sputter a bit before shutting down. If ignition problem it usually will stop suddenly.

If you have a known "good" spare coil on board try it and see if you have an improvement. That said, I caution against keeping a coil aboard as a spare if it not working correctly. If it turns out that the coil is the problem I'd buy 2 new ones and have a good spare.

MMI had a thread about coils on here just last week. Good info for you, I pasted it in below.

Originally Posted by Don Moyer View Post
There’s a technical matter that deserves our attention. Our faithful Web Shepherd is constantly looking behind every digital rock in cyberspace, to warn us of any “wolves” that might be threatening our flock from the outside. Currently, he’s frantically waving a red flag about reports of premature coil failures in the immediate aftermath of installing an electronic ignition kit. To be fair, I should point out that he has been waving this particular flag at least once or twice each year for the past several years, so the subject clearly deserves a closer look.


Electronic ignition systems (by design) provide a slightly higher dwell time within the primary circuit, which means that coils will normally operate at a somewhat higher temperature in an electronic system than they would in a comparable conventional system.

Technical representatives from Pertronix (the manufacturer of the Ignitor) continue to tell us that any good quality automotive oil-filled coil, with at least 3 ohms resistance in its primary windings, will work well with their Ignitor in our Atomic 4 application. There also seems to be agreement among other experts with whom we network that oil filled coils are somewhat more efficient in terms of dissipating the additional heat created in electronic systems than are solid epoxy coils (which is no doubt why oil filled coils typically feel hotter to the touch).

Epoxy filled coils are reported to have an advantage where high vibration is anticipated, or where a coil is to be mounted in any position other than upright. Oil filled coils apparently have somewhat of a tendency to leak oil from the bottom of their high tension post in any orientation other than upright. Solid epoxy coils are also somewhat more resistant to mechanical damage and the effects of corrosion in a marine environment.

Our own experience tends to support all of the foregoing rationale. Our experience also suggests that heat buildup is the most tangible threat to coil life, so the coils that we have been using and marketing for over 8 years are metal-jacketed oil-filled coils with 4 ohms of resistance within the primary circuit. They have been extremely reliable, in both conventional and electronic ignition systems, with a failure rate so low as to never have made it to our radar screen of concern.


In more recent conversations with the folks from Pertronix, we have gleaned the following information:

If your coil appears to be an original unit (perhaps 30 or more years old), has noticeable rust on the outside of the metal jacket, signs of mechanical damage or any indication that oil has leaked out of the metal jacket, it’s definitely wise to replace the coil. Realistically, it would be a good idea to replace such a coil, even if one were not installing an Ignitor.

Pertronix also recommends (as a matter of Ignitor reliability) that the current flowing within the primary ignition circuit should not exceed 4 amps. You can determine the current within your primary circuit as follows:

1) Measure the ohms of resistance across the primary terminals of your coil (with all leads disconnected).

2) Reconnect the coil leads, and ground the negative terminal of the coil with a wire of approximately 14 gauge. With the negative terminal of the coil grounded and the ignition switch on, read the voltage at the positive terminal of the coil.

3) Calculate the amperage within the primary circuit by dividing the voltage measured at the positive terminal of the coil by the resistance measured across the primary terminals of the coil. Example: 12 volts (as measured at the positive terminal of the coil) divided by 3 (the normal resistance measured across the primary terminals of a coil) = a maximum primary ignition circuit current of 4 amps.

NOTE: By comparison, the coils listed in our online catalog (with 4 ohms internal primary resistance) would result in only 3.5 amps within the primary ignition circuit, even if a high output alternator were installed to raise the system voltage to 14 volts.


1) We have no failure data to suggest that you need to automatically replace your existing coil, as long as it meets the criteria in the above recommendations from Pertronix.

2) If you do decide to replace your coil (for any reason), and vibration and/or concerns over corrosion are not a primary consideration, we continue to believe that a standard good quality, metal-jacketed, oil-filled coil is a very prudent choice.

3) For those of you who would benefit from the advantages of a solid epoxy-filled coil, or who would simply feel more comfortable with that option, we've added the epoxy-filled Flamethrower coil by Pertronix to our online catalog.

Best regards,

Don Moyer

1976 C&C 30 MKI

The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.

Last edited by Mo; 04-19-2011 at 01:44 PM.
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Old 04-20-2011, 08:47 AM
Possum Possum is offline
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engine stops

Thanks, I think you are right about the coil failing. The symptoms sound exact and the coil is an old one that was put on to replace a failed coil awhile back, by a friend who was working on the engine.
Besides, I am a classic old geezer with a classic old boat a classic case of coil overheating fits the picture to a "T".
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Old 04-20-2011, 09:19 AM
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sastanley sastanley is offline
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Mo, I must have missed that article from Don. That is exactly what happened in my case..replaced the points with a Pertronix system, and wham!, 30 year old coil runs for 50 minutes or so and fails.

I have a Pertronix epoxy filled currently, I even mounted it off the engine block, and it seems to work great.

Good luck Possum...I think we are on the right track & a coil is a reasonably priced item.
"Twice Around" - '77 C-30, #511 with original A-4 & MMI manifold - SOLD!
"Holiday" - '89 Alura 35 #109 (no longer a two boat owner!!)
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