Neptune Opposed Twin Coil Conversion

[Buccaneer]

I attempted to install a Briggs and Stratton 392329 (points / condenser style) coil
on my Neptune OB64A, twin opposed, 6hp, and have very weak spark.

The points test good, as does the kill switch. It has a new capacitor installed.
I hooked it up to the (Very Cold) Stevens tester a while ago, and
it doesn’t start firing until it reaches about 3.5 amps.

I find no specs for this coil in my Stevens or Merctronic data.
I did not think to reverse polarity on the primary test leads to see if that
makes a difference in the firing amps, but may re-test the coil again
when the garage warms up.

I grounded one of the secondary leads while testing. This coil
appears to only have one primary circuit.

Anyone have any ideas on the specs for this coil, or if I’m possibly
testing it incorrectly?
Thanks.

Prepare to be boarded!

[jcrigan]

You should be able to get a good spark between the two secondary leads. I don’t know if the secondarys are grounded on this coil that you are using. The secondaries on the neptune coil are isolated from ground. How is the magnet on your flywheel? Is the laminations close enough without touching the magnets?

[RICHARD A. WHITE]

Is this the Eismann Mag?

http://www.richardsoutboardtools.com
classicomctools@gmail.com

• This reply was modified 5 years, 2 months ago by RICHARD A. WHITE.

[Mumbles]

Are you sure that 392329 coil you’re using is meant to be used with a points type ignition?

I use the same coil in my 19 and 21 horse opposed Briggs mowers and they have pointless ignition systems. The coil has a module built into it, something like an Atom.

Here’s a link to the coils I’m using: Same P/N.

https://www.amazon.com/gp/product/B00G990HLS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

[Buccaneer]

jcrigan wrote:

You should be able to get a good spark between the two secondary leads. I don’t know if the secondarys are grounded on this coil that you are using. The secondaries on the neptune coil are isolated from ground. How is the magnet on your flywheel? Is the laminations close enough without touching the magnets?

My flywheel magnet has good pull. I believe the lams are close to the flywheel. I had
to bump them in a little as they were rubbing at first.

Prepare to be boarded!

[Buccaneer]

RICHARD A. WHITE wrote:

Is this the Eismann Mag?

Yes, the Eismann 72 magneto. Old coil secondaries were “open”

Prepare to be boarded!

[Buccaneer]

Mumbles wrote:

Are you sure that 392329 coil you’re using is meant to be used with a points type ignition?

I use the same coil in my 19 and 21 horse opposed Briggs mowers and they have pointless ignition systems. The coil has a module built into it, something like an Atom.

Here’s a link to the coils I’m using: Same P/N.

https://www.amazon.com/gp/product/B00G990HLS/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Mine is not like yours. Mine is “old school”. It looked new, and came in an original box, but appeared to have been mounted
at one time. It tested okay with an ohm meter.
I tried testing it on the Stevens again, switching the polarity. It still does’t fire until about 3.5 ohms.
Would it matter what position the B&S coil is mounted on the Eisemann laminations?
Thanks.

Prepare to be boarded!

[Buccaneer]

Mumbles wrote:

Are you sure that 392329 coil you’re using is meant to be used with a points type ignition?

I use the same coil in my 19 and 21 horse opposed Briggs mowers and they have pointless ignition systems. The coil has a module built into it, something like an Atom.

Here’s a link to the coils I’m using: Same P/N.

Mumbles, What would it take to convert said Neptune to “pointless” ignition using the B&S
coil you refer to? Possible?

Prepare to be boarded!

[RICHARD A. WHITE]

I can recommend 3 options,
Replace with known good OEM coil, Been there done that..

Replace with OMC coils, this swap has been covered and can be found in a previous Outboarder, I recall Jim Moffatt did the article and I supplied some photos.. Been there done that, got pics to prove it
Replace with a Speedifour coil.. They are close… I just did one I think it was the Speedifour coils…
I have the last conversion on my bench, makes good spark.

I can offer to convert for you, the issue being, I will shortly have no power head and flywheel to check for spark, as I have sold my Mastertwins. They are still here but spoken for.

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[The Boat House]

Richard, Is that the one where you stagger
cut the Laminates for the OMC style coils?

[Author]

Posts