Magnapower II Question

[Glastron_V210]

Hi there all.

I have a 135hp chrysler with Magnapower 2. I looked up the serial number and it's supposed to be a 1975. It's a one coil per cylinder ignition. It's a BD type.

I have a 1 bad ig coil. The replacement part number seems to be a R474475k2, but I can't find a pic of one to be sure.

Will a replacement coil for the sister Magnapower CDI system work?

Like this one:

http://cgi.ebay.ca/Coil-Ignition-Ch...at_Parts_Accessories_Gear&hash=item5641b0e5ec



I've read up on CDI coils, which are supposed to have higher resistance and lower inductance primaries, so it seems like any cdi coil should work?


Thanks for any and all opinions.

Chay

 

[lucas_chrysler_1]

Re: Magnapower II Question

not even close to the right coil. these mag. II systems were known as a problematic system. 2 of the coils run off of a positive groung, the other 2 are negative ground, if you are absolutly sure you have a bad coil (have checked stator, trigger, all connections, grounds, the actual spark plug wire, and are 100% sure) private message me and i can get you a coil through mail. but i need to know if it is a positive ground coil or a negative ground coil. what stats/or province do you love in? or try Frank A. he is an expert in these motors.

 

[Glastron_V210]

Re: Magnapower II Question

Thanks for the kind offer.

I found a couple of used ones at Franz Marine. Franz is very helpful.

The cdi is running the coil primary properly. I actually was able to obtain a spark from an automotive coil subbed in the cdi coil's place, so I know the primary is getting tickled. This means the trigger is ok. All other cylinders are sparking well, so it's just the one coil.

I've heard of many issues with this ignition, but this is the best running 2 stroke I've ever come across. Hard to believe there are so many issues.

Anyway, I think I'm ok. I read up on the ig. output and it seems to be +-280V from the CDI. I'm going to 'scope it to be sure. I think any CDI coil rated for this primary voltage should theoretically work, but I've read CDI coils have high primary resistance, and act much more like transformers, rather than inductive kickback/points schemes we are all familiar with. CDI's are supposed to have higher primary resistance (no numbers quoted though). But, when I measure a good coil primary I get .1 ohms. So maybe it's .1 instead of .01 or something. It's hard to find info or specs on this stuff...very difficult to make a reasoned decision on a substitute.


Chay

 

[Glastron_V210]

Re: Magnapower II Question

The pos/neg ground thing is very interesting.

I wonder what would be the effect of hooking up a coil backwards (as long as the primary is isolated from the mounts...I have to check this out). The current in the primary would go the other direction, and the secondary output voltage would be the opposite polarity, thus the current flow would be opposite...wasted spark arrangements have no issue with this.

Puzzling.

Chay

 

[Nordin]

Re: Magnapower II Question

The resistans on the coils for MagII should be primary about 0,1-0,5 ohm and secondary 500-600 ohm. Coils to CDI ign. system have normaly lower resistans at secondary then magneto with points. Magneto 6-8 kohm secondary. I think you can use a coil from a distributer battery ign. Chrysler Magnapower. The only thing is that these coils have no holes for mounting. But to measure the resistans at the coil is not 100%. I have a 60Hp with MagII and one coils readed 0,1 ohm primary and 550 ohm secondary but it did not work. I think that the primeside of the coil was shorted. My instrument FLUKE 23 measure shorted as 0,1 ohm likely 0,1 ohm as right resistans.

 

[Glastron_V210]

Re: Magnapower II Question

Well, I got a bit more interested in these coils. Warning, not banwidth friendly!

Is there two types of coils or just one. How can I prove if they're ok? How can I find out some more specs on the coil?

Resistances:

Pic 1355 is the primary resistance, about .4 with this meter

Pic 1357 is black lead to mouting hole 1: infinite
I did the same for all other leads and both mounting holes: all infinite

Pic 1362 is the high tension (secondary) to primary to black (140 ohms or so)

Pic 1363 is ht to primary white...about the same, which is should be!

 

[Glastron_V210]

Re: Magnapower II Question

Now the interesting stuff.

I decided to try a 'flick test' which is where you flick a battery on the primary, and measure secondary volts. This will tell you turns ratio, polarity, and whether the coil is intact. This requires a scope. BUT, if you just want to know if the coil is intact, a 100+ dc voltmeter will work:

PIC 1364 is the setup. Basically I used a 1.5V AA battery. The common of the battery is connected to the common of the 'scope, and the black primary lead of the coil. Channel 1 is connected to the white of the primary, and channel 2 to the ht output. The battery + will be 'flicked' against the white primary lead.

PIC 1365 is the result:

The top channel, channel 1 runs up to 1.25 volts and then decays as the primary current picks up (The battery can't sustain the current level 'cause it's tiny)


The bottom channel, the output, runs up due to transformer action, to 75 volts or so. This makes the turns ration somewhere around 75/1.25 = 60. I would have expected higher to be honest. This means for a 250V primary, the secondary only hits 15000volts. Perhaps there is some loading on the secondary that the little battery couldn't drive? Not sure.

Pic 1368 shows where the test coil was taken from..It the second one down, coil #2 for #2 cyl. So, then I pulled the #3 cyl (missing in photo) and tested it...

That's pic 1369. The results are the same. Same shape, same levels.

Conclusion: The Chrysler diagram showing + and - connections on the coil swapped for the #3 and #4 cylinder is in error. The coils are the same, and they are all hooked up the same way (Black ground), just the polarity of the driving voltage is different from the CDI unit.

I you want to do this test with a voltmeter, connect the neg of the voltmeter to the black lead, the pos of the voltmeter to the ht lead (Use a bolt to get it out of the connector hood), and flick a battery between the primary leads, neg to black, pos to white. The meter should delect pos when you make the connection, and deflect negative when you release. It's easiest to see with an analog meter.


Chay

 

[Nordin]

Re: Magnapower II Question

Hey! But thats not a MagII ign.system, thats a Prestolite system. If your engine is a 1975 it must been change to a Prestolite system. Chrysler did that during warrenty and made a retrofit kit. I am not so good at the Prestolite because i have not worked with it. I have had a 60Hp with that system but it allways run without problem. Check out at outboardignition.com they have troubleshouting chart fot that system.

 

[Glastron_V210]

Re: Magnapower II Question

You're F'ing kidding me!

Serious?

No kidding, r u sure? 'cause i think I ordered 2 of the wrong coild even though i sent a pic of the coil to the parts guy. Do they look similar?

Anyone have a pic of the two systems side by side?


Thanks for the world changing tip Nordin!

Chay

 

[Glastron_V210]

Re: Magnapower II Question

NUTS!

Nordin, you're bang on.

I couldn't find a pic of the Magnapower II, but I found a couple of the Prestolite:

http://forums.iboats.com/showthread.php?t=475585&page=1

for example, and it's a dead ringer.

I revised my order...guess the kiddies will have to wait a couple more days for knee boarding.

Thanks to all.

Chay

 

[Nordin]

Re: Magnapower II Question

I am not kidding you I am pretty sure. The MagII hade everything except the ign.coils under the flywheel. The ign.coils where mounted under a cover at the top of the powerhead. Also the plugs where under that cover. Hope you are going to run you engine with new coils.