Which coil

[airshot]

OK in a previous post I talked about a coil overheating problem and need to replace the coil but want to be sure I get the correct one. My 1983 3.0 Mercruiser was converted to electronic ignition (no points) by the previous owner so I have no instructions. I do know that it uses a 12v without a resistor wire. I believe the unit is a pertronics unit from the markings but cannot be positive. I replaced the coil a little more than a year ago and it is bad once again so perhaps I did not have the correct one. I would like to ask the good folks on here what would be the recommended or the proper coil for this engine. I looked up coils but am a bit confused over the different specs on these coils as I am no electronics whiz. Thanks in advance for your most welcome input.

 

[stonyloam]

I would recommend a flamethrower coil if you have a Petronix. Depending on which you have Ignitor, or Ignitor II. What is the number on the module, and is it red, or black?

 

[alldodge]

Get one which does not state anything about needing an external resistor

 

[airshot]

The module is black in color, thanks for responding. I have read a lot about the flamethrower but not sure which model, I believe three are listed on the site I looked at.

 

[airshot]

The module is black in color, thanks for responding. I have read a lot about the flamethrower but not sure which model, I believe three are listed on the site I looked at.

 

[airshot]

Sorry about the double post, things are still not quite up to par. Alldodge.... that is what I purchased the last time, just a non resistor coil and it only lasted a little over a year so I was hoping to get one that was the correct model as I am not sure the last one was the right one or not even though it worked for a while.

 

[stonyloam]

OK, if it is a Petronix, and if it is black you have the Ignitor. That being the case you have two options: either the Flamethrower 40,000 volt 1.5 ohm, in which case you would keep the resistance wire in place and connect the red Petronix wire directly to the purple choke wire for a. full 12 volts to the module, or the 3 ohm coil where you would replace the resistance wire with a stranded copper wire spliced into tne choke wire. In that case you could then just connect the Petronix red wire to the coil +. Either oil or epoxy should be fine. Here: http://www.pertronix.com/catalogs/pdf/ptx/2012/ptx2012_coils.pdf

 

[airshot]

Thanks for confirming what I have been reading. Already have the resistor wire bypassed from the previous coil. I was not sure of the "ohm" meanings but have a basic understanding now. Once again many thanks

 

[achris]

Ohms, named after Georg Ohm, is a unit of resistance. Ohm also defined the most basic of all electrical formula, Ohm's Law. Basically one ampere (a unit of electrical flow, current, named after André-Marie Ampère ) will flow through a resistance of one ohm when one volt (a unit of electrical pressure, voltage, named after François-Marie Arouet, aka Voltaire) is applied. The equation looks like I=V/R... Almost all DC electrical theory can be related directly to hydraulic theory, so if you are more familiar with hydraulics than electrics, here's how it goes.

Voltage is pressure.
Current is flow.
Resistance is, well, resistance.

If you think about that, and the how it affects things....
Higher voltage/pressure needs thicker tube walls/insulation to stop it leaking out.
Higher current/flow needs bigger tubes/wires to carry it.

A resistor is a flow restrictor. A diode is a check valve, complete with a 'cracking pressure' (in diodes that's called the forward bias voltage). A relay is a pilot operated check valve and a transistor is a servo valve. A capacitor (the old name is 'condenser') is an accumulator.

HTH,

Chris.......

 

[airshot]

Achris, thanks for the explanation, as a toolmaker by trade I can make just about anything.......as long as it isn't electrical. However your comparison to hydraulics does make it a bit easier, Thanks