Electronic Ignition and resistor

[Tacklewasher]

Was reading a thread below (while, it's below right now) about a motor dieing and it was suggested to switch to Electronic ignition so you can get rid of the ballast resistor.<br /><br />Well, I have the electonic (Petronix) but still have the resistor. Would I gain anything by losing the resistor or do I need to replace the coil and change heat range on the plugs as well?

 

[metwrench]

Re: Electronic Ignition and resistor

The resisitor in the system has Nothing to do with the " Electronic Ignition Triggers " , It has to do with the Ignition Coil Operation Voltage.<br /><br />Some coils are " External" resistor types that need 9 volt feed to operate long term. Internal Coils are fed constant 12 Volts.<br /><br />How the Internal coild works is just feeding battery Voltage direct and away you go.<br /><br />The 9 Volt External types get fed 12Volts ONLY during Start up, Then when the Ignition is turned to the RUN position, The doping resistor drops the Voltage to 9 to run the engine. <br /><br />If you take out the resistor, and the coil is designed to run on 9 Volts, It will probably run ok for awhile, But when it heats up the coil Windings will start to Overheat and the Spark will break down ( engine will sputter and Die )

 

[pecothern]

Re: Electronic Ignition and resistor

Tacklewasher I'm was wondering what type of engine and setup you have I was under the impression that ballast resistors were only used with point type ignition. Allowing you to use a lower volt coil to increase the point life and bypassing the resistor during cranking to get full twelve volts to the coil when cranking only. The situation I had was a burnt-up coil that said on the coil "Must use external resistor" but I have no external resistor. I had twelve volts to the coil all the time 92 5.7ltr OMC I bought the boat used but the original owner says he never changed the coil. I put a straight 12 volt coil on it and the spark is very hot and runs great now. The rating of how hot the plugs are goes along only with the temp the engine is running most marine application run much cooler than automobile. Marine engines run 160-180 Degrees therefore need cooler plugs than a car. Cooler plugs have longer porcelian on their tip to disperse the heat.

 

[Tacklewasher]

Re: Electronic Ignition and resistor

The motor came with points (1975 OMC 120 HP I/O) but I put a Petronix Electronic Ignition on it.<br /><br />I did not change the coil so I assume I have a 9 volt coil and I do have the external resistor. I've been wondering if I should change the coil and go to a 12 volt without the resistor.

 

[metwrench]

Re: Electronic Ignition and resistor

I wounldnt assume anything with the coil Voltage. You can easily test it with a Volt meter. Start the engine, Volt meter lead to Ground and one to the Positive side of the coil, see what you have.<br /><br />Coils are manufactured to run on 9V or 12V, It doesn't matter which coil you have, Both CONVENTIAL style coils run Max Outputs of around 12KV. Now if you have a GM Style Motor, You can put an HEI Distributor in it ( High Energy Ignition ) this is the GM Distributor with the large Cap and Coil Mounted on top, ( 50 KV Output ) Ford has Dura Spark, depending on year ( 80 KV output )<br /><br />If I had this Prestolite Ignition in my boat, and I wanted a " Hotter" Spark, I would Contact the prestolite Dealer I bought it from and ask for a reccomendation. If they Dont give one, Go to a Performance Coil that produces 40KV Plus Volts. Use a Convential Type ( Like your old one ) By the way Guys, Thruth be known ? Points actually make the coil Produce Higher Outputs, But thet are sloppy on timing and the obviously wear out. Also keep in mind Spark Plug Gap, Circuit Resistance ( Spark plug Wire sizes, and LENGTH ) play a BIG Part in Ignition output !! Suggestion for everyone, Always try to use an 8mm Wire on your boats !<br /><br />John