Pertronix ignition in 470 and locating resistance wire

[Benny67]

Anybody have an idea on how to find this wire's location or if it's a plain old resistor where it might be hiding?

It's a Carver boat if that helps...I'd assume it would be similar in most boats

 

[Fishermark]

It is the wire leading to the + coil. It is usually spliced in somewhere between the electric choke and the coil. Simply bypass that wire if you are adding Pertronix and changing the coil.

 

[stonyloam]

Yeah it is the purple wire going from the electric choke connector to the coil +. Replace it with a piece of 14 ga stranded wire. You can splice into the wire at the choke connector. Boat brand is unimportant, Mercruiser is Mercruiser.

 

[Benny67]

I googled a schematic for a 470 wiring configuration and found one.

My manual does not include a basic wiring diagram or I wasn't looking hard enough.

I was basically wondering if there was a ballast resistor hidden somewhere I might have missed.

Stony,

Why 14AWG? The wires on the coil appears to me to be 18AWG. I doubt it will see 5 amps of current. Why go up in size?

 

[Fishermark]

You can use a smaller gauge - but you are only talking about a foot or two at most of wire. When it comes to wire, I always err on the side of using a larger gauge. You can't go too large, but you can go too small. You don't want a voltage drop at the coil / ignition. (I can't speak for Stony - but that's my 2 pennies).

 

[Benny67]

If you check your open air current ratings for 14awg VS 18awg the difference is only around 1.5 amps. I just assume stick with the original configuration.

Besides, the 12Vdc feed to the coil is a relatively small current draw.

As far as a difference in resistance it's insignificant...you would create more of a voltage drop via a bad crimp or loose terminal vs the difference in the two guages.

 

[Benny67]

Some people might think because you are dealing with a coil that produces 40KV that you are going to draw a boatload of current....not the case in this type of circuit.

 

[wrestling coach]

One sure way to identify the resistance wire besides being purple (mine was more pink due to age) is that it will be a SOLID wire not stranded wire.

 

[Benny67]

i'll look for it this weekend and also confirm the wire gauge.

I have 2 engines to do so hopefully it will go off without any troubles and I can then call the mover to come and drop me in the water before next weekend.

 

[Bt Doctur]

http://www.boatfix.com/merc/Servmanl/13/13E4R2.PDF

 

[Bt Doctur]

 

[Benny67]

BT,

Thanks for digging that up

 

[stonyloam]

I googled a schematic for a 470 wiring configuration and found one.

My manual does not include a basic wiring diagram or I wasn't looking hard enough.

I was basically wondering if there was a ballast resistor hidden somewhere I might have missed.

Stony,

Why 14AWG? The wires on the coil appears to me to be 18AWG. I doubt it will see 5 amps of current. Why go up in size?

The (purple) resistance wire IS the ballast resistor. 14 ga stranded is what Petronix recommends.

 

[Benny67]

i'll just replace it with whatever gauge the resistor wire gauge is and end it at that.

This whole project of getting this boat up and running for the season has been a pain in the...well you can figure it out.

 

[chris mig]

So glad I read this post as I am about to do the same thing this weekend on a 485 which has the same basic wiring. I did not think I needed to do anything like this wire replacement, if someone could explain the basic point of this replacement of a wire that looks no different than any other wire on my motor I would appreciate the knowledge and if in fact I do need to replace it at all thank you. dont mean to hijack this post but seems to be a good place to ask the question BTW I am only replacing the points and not the coil is this ok?

 

[thumpar]

If you are not changing to a ballisted coil keep the resistance wire and only put the full 12v to the pertronix. There are diagrams included with the pertronix unit. When I did mine I changed the coil at the same time and bypassed the resistance wire to make it easy.

 

[chris mig]

OMG it cant be easy where do i grab the 12v from for the electronic ignition as my paper work is at the boat do
i splice in at the choke?

 

[stonyloam]

OK Chris I'll give it a shot. The coil circuit in your engine should have a total resistance of about 3 ohms. The resistance limits correct flow which keeps the coil from getting too hot. You get about 1.8 ohms fram the resistance wire and about 1.5 ohms from the coil itself. OK so why not just use a 3 ohm coil you ask? Because when you are starting your engine your coil needs a "boost". When you start your engine you are putting a tremendous drain on the battery which drops the voltage, so during starting the coil ( in your case with the 470 engine) gets full battery voltage from the slave solenoid, and the resistance wire is bypassed. Once the engine starts the battery voltage goes back up and when you release the key back to run, the coil gets its voltage through the resistance wire. So you DO NOT replace the wire with a conventional points system and stock coil.

 

[stonyloam]

Just that easy, splice into the purple wire coming fron the ignition to the choke.

 

[chris mig]

Thanks Stony I did some reading as well as your post, and fully understand the system now. In your opinion is the 12v coil any better,with the 40,000 output by pertronics?
I should ask is there a big performance gain/fuel economy?