View Full Version : Ballast Resistor Question

05-14-2006, 09:30 PM
I have an 88 Mastercraft Prostar and have had it about a year. When I originally purchased the boat, it had problems starting and the ballast resistor was the issue then.

Now I am having problems with it starting after it's been running a few hours. I thought it might be the resistor again, but it seems to be alright. I was wondering if I understood how it worked since I think it may be the solenoid on the starter that sends the 12V to the coil when starting...

So - there are 2 orange wires connected to the solenoid and 2 purple on the other side.

The two purple lines going into the solenoid are the power to the resistor and makes it so that it goes through to the coil. When starting, the second orange wire is also active - sending a direct current to coil. Is this correct?

Reason I ask is when I disconnect the orange wire altogather and test if it sends volts down the wire - it was totally dead.

Sorry for the long message - but should that orange wire be have volts on it when starting? I thought the starter usually sends extra volts to the coil when starting - how does it do this?


05-15-2006, 02:09 PM
That is correct. If you look at your starter solenoid you will see an orange wire attached to a terminal on the opposited side of the wire coming from the ignition. The purpose of the orange wire is to provide a full 12 volts to the coil when the key is in the 'start' position. It simply bypasses the ballast resistor. It should be attached to the + side of the coil. It will provide no power when the key is in the 'run' position.

I would seriously recommend upgrading to an electronic ignition system. They work much better and are essentially maintenance free.

Not sure if that helps or not. Good luck.


05-15-2006, 05:24 PM

05-15-2006, 07:01 PM
Hunterb is correct.....Best $100.00 that you can spend....

I agree 100%!!!!!!!!!!!!!!!!!!!!!!!!!!!!You wouldn't get that much performance out of one of UMP's groupie/hookers!

05-15-2006, 08:41 PM
Hunterb is correct.....Best $100.00 that you can spend....

Is it only 100 dollars to upgrade. What would I need. It looks like on skidim, the kits cost 500 bux:

What do you guys recommend.

05-15-2006, 08:50 PM
or is it this:??

05-15-2006, 08:51 PM
That is a whole new distributor. What you need is here.

05-15-2006, 08:56 PM
Ooops.....just a little slow on the post. That is the kit that you want. Check what distributor set up you have and let Ski DIM know..... they'll hook you up with the right parts for the job.

05-16-2006, 09:49 AM
I just upgraded to an electronic (breakerless) ignition, on my í90 PS 190 with prestolite screw down cap distributor, with a Malory set up, PN MAL9-26902. Much of what I read on this site instructed removing the ballast resistor, but the instructions were very clear with this upgrade kit to leave it in place. I also replaced the coil (cheap) with one specified for a electronic ignition. (It started right up but I havenít run it on the water yet.) Can somebody clear up this ballast resistor- no ballast resistor question??

05-16-2006, 12:26 PM
My understanding of the ballast resistor is that it is used on ignition systems with breaker points. It reduces the voltage from 12 (approx) to 9.5 (approx). I believe the reason it does this is to reduce the wear on the points and allow them to function for a longer period than if they were receiving a full 12 volts. I think the theory is that once the motor is up and running the 9.5 volts is enough power for the motor to run properly. During start-up, when the motor can benefit from a more powerful spark, the ballast resistor is bypassed (by the orange wire coming from the solenoid on a mastercraft) and a full 12 volts is fed through the points.

If you follow this theory then the ballast resistor serves no purpose on a system that has had the points removed. I would also suggest a good 12 volt coil be added.

Having said all that, which may or may not be correct, I would follow the instructions of the manufacturer of whatever system you are installing as they should know how it works best. So I would leave yours as is Wakeboy, unless someone has solid information to the contrary.

Also Ben, the system will work fine as is, it just needs a lot more attention to keep it in peak performance. If money is an object, then set your points up correctly and just be prepared to file/replace/adjust them a few times over the summer.

Good luck


05-16-2006, 03:14 PM
It has to do with coil saturation and potential overheating of the coil. Thats what ballast resistors prevent.
When you switch to electronic ignition, the module controls dwell time (saturation) and prevents the coil from overheating.
During starting, if the starter system and battery are all in good shape, the voltage will drop to approx. 10 v. during cranking. Bypassing the resistor during starting eliminates the reduction in current (at already reduced cranking voltage) by the resistor and should provide a reliable start.

05-16-2006, 04:38 PM
Bruce and everyone else,

Thanks for all the help. I will call SkiDim and let them know what I have and order one that doesn't run on points. Sounds like that's the way to go if the money isn't an issue. As Wakeboy did, sounds like I should go ahead and get a new coil made for the system as well...