Neptune magneto question(s)

[tibor]

Hello masters of old outboards!

I have a Neptune 15A1 and an AA1A (1945 and 48) that I just recently acquired. I am not getting a spark in either one. I am not experienced with old magnetos at all, so this may be a trivial question….  however I am reasonably experienced in electronic hobby projects so have a bunch of tools to measure things…

I believe both circuits are correct, nothing is accidentally shorted to ground, etc.  Here is what I measure on the coils and condensers:

Coil 15A1 primary: 0.6 Ohm resistance, 0.73 mH inductance,
Coil 15A1 secondary: 4.8 KOhm, 8.2 H inductance,

Coil AA1A primary: 0.9 Ohm, 3.12 mH,
Coil AA1A scondary: 5.0 KOhm, 9 H inductance,

Condenser 15A1:  217 nF, 180 Ohm ESR,
Condenser AA1A:  215 nF, 1.4 Ohm ESR

Do these numbers look reasonable? I think that the coils are probably good, even though 8 Henry is a very large number for me, who is used to small transformers.

Those ESRs are suspect (to me) on both condensers, even though they match nicely to 0.22 uF capacitance. So I guess my question is, what should I replace first? 🙂

Btw, as I am taking these outboards apart, I cannot help but love the simplicity and elegance of their design.

Thanks a lot in advance for your guidance.

[Sam M.]

I have absolutely no clue about what any of those readings should be, but good troubleshooting advice is to check the simplest things first.

Here are some ideas for simple checks before replacing any parts:

• Are the sparkplugs gapped reasonably?
• Do you have a good ground when checking for spark?
• Are the points clean?
• Is the spark plug wire still in good shape? (No internal or external breaks)
• Are you spinning over the motor quite quickly when testing for spark?  There are ignition systems which work fine when the motor is running but won’t spark if the motor is being spun over too slow.

Hope this helps!

[tibor]

Sam, thanks for the quick reply.

I tested with an inline spark tester both with the old and a new plug. I did check the gap on the new plug (0.025). I will clean the points more, not sure what I am looking for. So far I did like 4-5 gentle strokes with some fine sandpaper.

The plug wires are not looking too good, one of them has the boot all cracked up. I will try with a new plug wire again.

For the test I cranked the engine with a pull cord.

[Author]

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