Some Comments About Coils

[smosher]

to calculate amps the formula is voltage / resistance(ohms) = amps

14.2(output from Alternator) / 3.5 (coil resistance) = 4.05 amps

The Pertronix coil states is has a resistance of 3.0 ohms which would make
the amp draw of 4.7.

The Pertronix Web site does say 4 and 6 cyclinder engines should not exceed
4 amps. I would of thought that if this was the case then they would of designed the coil for a higher resistance instead of adding a ballast resistor.

[67c&ccorv]

to calculate amps the formula is voltage / resistance(ohms) = amps

14.2(output from Alternator) / 3.5 (coil resistance) = 4.05 amps

The Pertronix coil states is has a resistance of 3.0 ohms which would make
the amp draw of 4.7.

The Pertronix Web site does say 4 and 6 cyclinder engines should not exceed
4 amps. I would of thought that if this was the case then they would of designed the coil for a higher resistance instead of adding a ballast resistor.

Smosher - are you saying that the Pertronix coil has a "ballast resistor" that must also be connected to the ignition circuit - or do you mean a ballast resistor must be added to the circuit in the above example in order not to exceed 4.7amps?

If so, what would a schematic of the circuit look like?

(I was under the impression a ballast resistor is added to a 12 volt ignition circuit to reduce the current to 6 volts when using a 6 volt coil so as to obtain an adequate spark when starting the motor.)

[smosher]

I have the pertronix coil and it didn't come with a ballast resistor.

I should measure the coil but if the 3.0 ohm coil is actually 3.5 or greater then it would be close enough to 4 amps. I'm kinda literal so when I see 3.0 I assume 3.0.

A ballast resistor would go between the ignition switch and the + side of the coil

Steve

[jayw]

Don, thanks so much for this thread (and all of your other bits of wisdom)- once again, you saved me lots of anguish and expense.
After motoring for about 4-5 hours, my trusty A4 just stopped. Checked the fuel, found some crud in the Racor, installed new filter, drained gas from carb bowl, removed and cleaned jet, restarted, and thought "that was easy".
About 1 hour later, engine quit again. While scratching my head, I recalled this discussion about coil failures and after a bit of observation, satisfied myself that coil overheating was indeed the problem.
One interesting twist that I can't figure out is that with the faulty coil, there was no charging of the batteries by the alternator (found this a bit later when I got a low battery alarm while engine was running) but BOTH problems were fixed when I installed a new coil.
How is charging related to coils? I didn't change or replace any wiring, just hooked existing wires to the new coil.
Thanks again for your invaluable interest and services.

[Don Moyer]

It may be because it's so late in the day, but I can't think of a single explanation for how a coil would be involved in a charging issue. Fortunately there is a lot of electrical expertise now on the Forum that is hopefully even now swooping in to enlighten us.

Don

[67c&ccorv]

Don, I managed to leave my ignition switch on for several days...yep, I am definately getting older!

I returned to the boat and after discovering I left the switch "on" (my on- board charger kept the batteries charged) attempted to start the motor. Normally it started on the first turn of the engine but after 3 tries concluded I must have damaged either the ignition module and/or the Pertronix Flame Thrower coil.

I replaced the ignition module as routine and then checked for spark - it appears orange couloured and weak and the motor still won't start. Fuel is flowing to the carb and I am getting a nice fuel vapor from the plug holes if I rotate the motor with the fuel tap on. (Something I don't do for long after having a similar experience with my 1975 Norton Commando where I started a beautiful fire at the plug hole whilst testing for a spark!)

Any thoughts on whether it is time for a new coil?

PS - I think my description as a "senior member" particularly appropriate at this time!

[rigspelt]

While awaiting Don's reply, maybe I can chime in with a couple of thoughts. Might be a good idea to check the whole primary ignitiion circuit, to make sure no other electrical components overheated leading to poor electrical conduction. When we bought this boat and had it checked by a mechanic, the first thing he said was to install a high engine temp/low oil pressure alarm. It buzzes incessantly if the ignition key is left on. I got this one from MMI and it has been working great: http://www.moyermarine.com/cgi-bin/s...ey=KTAS_01_191.

[ndutton]

I have the same alarm system as Rigsy with one additional component, a delay-on-make relay. Once the ignition is turned on, the alarm system doesn't arm until 10 seconds later allowing me to start the engine without any initial alarm noise. Here's where I found it:

http://www.mcmaster.com/#77055k63/=3pobtk

[Don Moyer]

Ccorv,

Whenever an ignition switch is left in the "ON" position a three-way struggle takes place between the battery(s), the coil, and the electronic ignition module. If the electronic module fails first, the coil and batteries might be saved. If the electronic module (or for that matter the points and condenser) hangs on, a good coil will normally win over the batteries and continue working till the batteries are gone.

Unfortunately, with shore power connected, the batteries hold a big trump card so the coil and electronic module are left to fight it out among themselves. In your case, it does appear that the electronic module hung on long enough to do serious damage to the coil through over-heating.

To build on rigspelt's point a bit, whenever an ignition switch is left in the "ON" position, the "soldering iron" concept sets up the possibility that the primary circuit itself can heat up over time and create damage to wiring below the current flow required to blow a protective fuse - even if a proper 20 amp fuse is installed in the circuit.

Don

[Mark Millbauer]

NDUTTON,
Thanks for the info on the relay. I am curious though as to how you wired it into the circuit. When I got "Solution" it would not start. Instead of an ignition switch and starter button, she has a regular momentary on type ignition switch and as a result, a small car type relay wired into the circuit. I was able to diagnose that the relay was bad and hot wired it. Even though I was able to find a generic replacement from NAPPA, I carry a little remote starter switch for when the new relay corrodes.
Do you have your timer relay wired the same way? In other words, is the timer relay suitable to serve as a starter relay as well as an alarm?

Mark
Cat 27, "Solution"

[Mark Millbauer]

Actually, as soon as i hit send, I think I answered my own question. You timer relay is just kicking on an audible alarm device. So on that note, does anyone know a good source for a marine type starter relay?

Mark
"Solution"

[67c&ccorv]

Thanks guys - Rigsy, I do have the temp-oil alarm system installed but have not yet wired it up

I better get started.

Send me a new coil Don.

[ndutton]

Mark,
I started a new thread about the alarm system that addresses your question.

Neil

[Boilerbob7]

Petronix web site

I recently purchased a Cataline 27 with an A4. I'm trying to order a 190-v2 ignitor as a spare, but for some reason the Petronix website is extremely difficult to find any parts. I type 190-v2 in their search with no results. Any ideas?

[ghaegele]

Buy from Moyer Marine. You will be certain to get the exact part your A4 needs. Order online or, even better, call and speak to Ken who can answer just about any question you have.