Re: How do I match condensers and spark coils?

[wmohat]

In reviewing the replies so far, I have the following observations:

1) JoeCB: yes, .22uF will certainly work. However, if the original condenser was supposed to be
.68uF, you will get FAR more voltage across the points when they open than you should.
(about triple). This absolutely will shorten the life of the points. .22uF is far better than
nothing, but ….I still think you should be reasonably close.

2) FrankR: The points open AFTER the voltage reverses, and the voltage spike hits maximum (or just
a few degrees later, when coil current is at maximum.) I took pictures on a scope,
and wrote a technical article on the topic. (I believe it will be published in The Outboarder
in October). If you read that article, I guarantee you’ll find more information than
you want to know on this topic.

3) George: Yes, if you get a coil from another outboard, you can look up the matching condenser for it.
However, what you do NOT know is the strength of the magnets in the flywheel, and the
mechanical size of the poles. You might get up to 4 times more (or 4 times LESS) voltage induced
in the replacement coil compared to your original, and that might well determine if the
original condenser is appropriate or not. You might well have to use a condenser of a different
size than was used in the original application.

********* I still think that when the points open up, you want to see about a 50 to 100 volt "inductive
kick" across the points. With NO condenser, the "kick" will be much higher (several thousand volts,
which will burn the points rather quickly). And, with too large of a condenser, you might only get 10
to 20 volts across the primary, which won’t give you enough voltage to generate a spark at the
secondary. I’d like to see some documentation from either a coil or condenser manufacturer,
that describes how to "size" a condenser correctly.

***********************************************************************
Bill Mohat MS/CIS, BSEET, CCNA

"You can avoid reality, but you cannot avoid the consequences of avoiding reality." --Ayn Rand **********************************************