Confirming Ignition upgrade

[tango13]

After a ton of research, I want to confirm my plan for my ignition upgrade before getting started.

On my 1977 Mercruiser "250hp" 350, Ill be doing plugs, cap, rotor, wires, Pertronix ignitor, and coil. Since the coil is externally resisted, I'm going with a new coil with a lower primary resistance (Flamethrower II - 0.6ohms primary). I'm doing this because I want to keep the external resistor wire, since I dont really like having wires taped off or cutting into the harness.. Sloppy! I think that should work, correct? That will get a total of 1.5 ohms at the coil, which I need. Then, I want to do the ignitor I kit. This is where it gets confusing. After reading all over the place, I find that people argue whether you MUST have a 12v source, or if you can run from the coil terminal with less voltage due to the resistor wire. Some people say pertronix units can work with lower voltage, some dont. Long ago, I installed a pertronix ignitor on my uncles '79 Mercruiser 228 (with the stock coil & resistor wire) and it worked fine.. That was before I knew anything about the resistance requirements.

Worst case sceneario, I run a new 12v wire from my key... I just didnt want it to come to that.

Can anyone confirm any of this?

 

[thumpar]

I would go with an internally ballasted coil and the Pertronix. Some people have gotten away with not running a full 12v but there always seems to be a hickup at some point. It is easy to find 12v. When I did mine I ran a wire parallel to the resistance wire and taped everything up. Some people just run it off the choke.

 

[tango13]

I would go with an internally ballasted coil and the Pertronix. Some people have gotten away with not running a full 12v but there always seems to be a hickup at some point. It is easy to find 12v. When I did mine I ran a wire parallel to the resistance wire and taped everything up. Some people just run it off the choke.

Whats your reason for preference towards to interanlly ballasted? The only reason I chose to go external was to mimic the the stock setup, although in hindsight If i end up running 12v, I guess I break that goal. I suppose I if I did end up doing the 12v, I could tie in a new external resisitor to the 0.6 ohm coil..

 

[thumpar]

The reason to go internally ballasted is so that you only have to run 1 wire and you get a full 12v to the coil and pertronix module.

 

[tango13]

Understandable!

 

[airshot]

If I may suggest, a few years back I had coil issues with a stock coil (non resister) on the pertronics ignition system. In fact I was going thru a bout two coils each season, always carried a spare. Thru some very good advice on this forum I switched to a flame thrower coil and no more issues. Far better quality and higher spark output. That was more than 2 years back and never had another issue since. Motor idles better and starts much easier and plugs burn cleaner.

 

[Fishermark]

I like the Pertonix okay - especially the Ignitor II - but since you are buying new everything, a much better alternative is to buy a complete GM Delco EST set up. You can shop around and find complete kits for around $240. Like this one pictured here: