View Full Version : Electronic Ignition Conversion - to coil or not to coil

03-23-2006, 09:41 AM
1990 Maristar 351W

Need some advice and the more threads I read the more confused I am. I have recently purchased an electronic conversion kit for my Prestolite distributor. Iíve seen that you donít need to worry about the coil, or that you do have to replace (or test it), or that you can bypass the ballast resistor, etc. For this year and type of engine, what have other people done? My boat is 2 hours from my house, so I would like to be prepared when I travel to perform that work.

Also seen that you must be more aware of your key position to prevent the module from burning out, donít leave it in the ďonĒ position if the engine isnít started. Some boats have a buzzing noise when the key is in the ďonĒ positions versus ďaccelĒ position if the engine is not running. Mine does not do this, but would be a nice modification to prevent being stranded with a burned out module. Any advice?

Thanks for any advice.

east tx skier
03-23-2006, 09:51 AM
Hoff, did you read BriEOD's how-to in the FAQ?

03-23-2006, 09:58 AM
Yes. Got a copy of the How To, but it doesn't refer to the ignition coil. I can check the coils voltage to determine what it is. But, if I bypass something versus replacing something, I would rather do that.

east tx skier
03-23-2006, 10:00 AM
Gotcha. I figured you had seen it. My boat came with electronic ignition, so I don't know a thing about the conversion.

03-23-2006, 10:07 AM
If you purchased the Prestolite Breakerless Electronic Ignition Conversion Kit, there are instructions in it at the end of the install, on a test that you or a qualified tech should perform to see if a replacement coil is needed and they give you the info. on the type coil to ask for if you need to replace the coil. It is the Prestolite 5-69 Electronic Ignition Coil, recommended for optimum performance, SKIDIM has them. I installed the works on our '89PS 190 351W and a friends 1990MaristaR 351W. I just re-read the entire instruction sheet and it does not warn of leaving the key in various positions and of any potential damage to the module as a result. Somewhere there is a previous thread concerning this conversion about 8 weeks back but I have failed to find it, so someone on here may want to post a link if the can find it. Hope this helps!

03-23-2006, 10:36 AM
As long as your coil is good there is no need to replace. You MUST bypass the ballast resistor.

03-23-2006, 02:01 PM
Thanks guys.

To bypass the ballast resistor, does that just imply removing it from the circuit completely?

03-23-2006, 02:19 PM
I am pretty sure that is correct. Just remove it from the circuit.

03-23-2006, 02:32 PM
Hey Hoff,

Yep, just cut 'er loose...when I replaced mine , I did the whole enchalada - ignition module and coil and plug wires and plugs (my choice on the wires and plugs) runs great... my motor's a bit different but the electronics are probably close...


03-23-2006, 02:48 PM
Yep, just cut it out and splice the wire back together.

03-23-2006, 02:56 PM
Nice, just what I wanted to hear. Now I just got to hope that my multimeter has the ohm-meter function to check out the coil.

03-23-2006, 03:33 PM

Kevin 89MC
03-23-2006, 06:06 PM
IIRC, the prev. owner that did my conversion just left the resistor in place, and attached both leads to one terminal. Just another way of doing things. You'll love EI.
Good luck.

03-24-2006, 07:24 AM
Ah, nice and clean way of doing it. Think I'll go that route. Thanks guys.

03-30-2006, 12:49 PM
I tried to check the resistance on my coil yesterday to determine if it is in good shape, but Iím not sure if I did it correctly. Do I need to completely take it out of the circuit to check correctly? (i.e. remove positive terminal, negative terminal and primary coil wire?). Or, can you check it with everything still hooked up?

03-31-2006, 07:47 AM
disconnect it

03-31-2006, 08:05 AM
Thanks tommcat, I didn't think to check it until I had installed the new ignition module, bypassed the resister and hooked up all the wires. Wasn't in the mood to disconnect anything. I was just wanting to sip some beers and cruise a little.

03-31-2006, 01:44 PM
The ballast resistor is used in a point ignition system to control the current flowing to the coil primary windings. With points, dwell time is not variable, and at an idle the coil could start to overheat and fail.
With the electronic conversion, dwell time is controlled by the module. Therefore you should eliminate the balast resistor to take full advantage of the modules ability to control and saturate the coil primary windings.
The difference between a stock coil with an aftermarket coil is the primary-to-secondary windings ratio. Since a matched aftermarket coil is designed to work in conjunction with the modules ability to control saturation, it can deliver more KV (Kilovolts, and if needed) across the complete RPM spectrum. This provides more potential voltage during the 2 most engine operationaly demanding times of engine start and WOT.
Also, some modules will shut themselves "off" if a trigger is not sensed within a specified amount of time (no cranking rpm sensed). You should be able to find this out by contacting the manufacturer on how they protect modules against overheat and burn-out.
So to sum it up, if your going to spend the money on electronic ignition conversion, go the complete mile (with a new coil) to get optimum performance. Why not? You've already spent the time, money and energy on the conversion.
Just my 2 cents worth...

03-31-2006, 02:33 PM
EricB, Nicely said, I knew there was a reason but couldn't have put it together like you did!

03-31-2006, 02:37 PM
Thanks for the info, a little over my head but very useful nonetheless.

You guys and your electrical mumbo jumbo. Iíll stick to the mechanical stuff. Much easier to know when something is going to knock you down instead of the invisible punch of electricity.

03-31-2006, 02:46 PM
Go ahead and get the coil also. The difference that it made my old '87 was drastic enough for even my wife to notice on her own.