I recently installed a Mallory magnetic distributor in my 502, and will power it with the Promaster coil. Mallory says if I don't use the supplied resister, it will burn out the module.
What would be the point in using a high output coil with a resistor? I know for a fact Thunderbolt ignition won't work with a resister. Just for the record, I'm not interested in using
CD ignition. Thank's!
Bob.

I'm replying to my own post. 78 hits and not 1 reply? Maybe I posted in the wrong category, or could be I joined the wrong boating forum!

All of my Mallory marine ignitions needed to use the supplied ballast resistor. The ballast resistor is used to buffer out high and low spikes to protect your ignition. It is not used to "lower voltage" and "weaken" your high output coil as you might believe. And yes, you probably would burn out your ignition if not used.

Also, I do believe you did post this in the wrong section at first. No need to get angry, it's just a forum.

I'm trying to understand your concerns.
The Mallory Promaster coil is designed to operate in a ballasted system, and so is the Magnetic module. Are you somehow thinking that running the system at 12v continuously will deliver some sort of performance advantage?
A traditional auto ignition with breaker points used a ballast resistor to lower AND buffer the coil voltage to maintain a magnetic field flux in the coil "between" firing episodes AND to lower the voltage to keep the coil from overheating (the coils were essentially designed to run on 9v or so continuously. During startup, while the starter is engaged, the coil and points operate at a full 12v to better deal with rich fuel mixtures when the carburetor choke was closed.
When electronic ignition triggers replaced points, it was still during the era of carburetors and chokes, so the "hot" spark while starting was beneficial so the ballast resistor was maintained.
When different types of solid state ignition systems were developed, it was determined that ballasting was necessary to protect the newfangled electronics. And since the ignition amplifiers were ALREADY having some trouble shedding heat, and ballasts also generate heat (from both the current AND the magnetic field under the half-wave quasi AC pulses), it quickly became evident that trying to build the blasting INTO the ignition amplifier was counterproductive when autos already have provisions for external ballasting. So - outside of a full race application, external ballasting simply makes good sense.

Now that makes a lot of sense! I'm an old timer and remember when a resister was used so as not to burn out the points. Gm used a terminal on the solenoid as a resister bypass when cranking. My mini starter also has that feature. I appreciate your advice, and I learned something new. I thought I was being ignored because I'm new to the forum. I really didn't want to get cross, but I figured it would get some ones attention! Thank's again.

Holy cow! Now I really learned something about ignition systems. My Vo-tech instructor never quite put it that way. I often wondered why my Thunderbolt system had no resistor, and I'm talking a none computerized engine!

The Thunderbolt IV/V module will burn out with a coil with less than .7 ohms resistance. There are plenty of coils to choose from that have .7ohms to .9ohms. Anything more than this will defeat the high energy purpose of the Thunderbolt system.

The Tbolt module ramps up dwell to the coil as the rpms increase. This is same practice HEI modules use. If a system can not change dwell - ie: systems that typically use ballast resistors or high internal resistance - , then if enough is used for proper higher rpm use, it can burn up things at low rpm. If it has little enough dwell to not burn up things at low rpm then it may not have enough at higher rpms and load.

Anyway, anything with a module is designed around a certain coil primary resistance. Again, in Mercruiser's Tbolt IV/Vdesign parameters, it is .7 ohms.

So, since you are using a different ignition system, use a coil specified for use by , or same resistances set forward by them.