Coil Testing for Johnson HD25

[Stewart Mayer]

Hi, I’m working with the students who you might see posting on here, I have 16 students fixing up 8 motors… Thank you AOMCI admins for setting us up!

We have a 1947 HD25 and had spark from one plug but not another.  We took out the coils to put a meter on them, and compare them, to see if we can find any differences and try to locate the problem.  Attached is a photo.  I have some experience, but not a lot, so we could use some advice.

In the photo, I assume C/D are the primary coil, and A/B is the secondary.  On both coils, C/D reads about 1 ohm, so it has continuity.  But I can’t get any reading from A/B on either coil.  Is this normal? I’ve tried two digital ohm meters, but I’ve read an old analog meter might be best.

Thank you!

[Stewart Mayer]

I’ve got a follow up question, I’ve read some posts that say to use solid instead of stranded spark plug wire.  It seems to me, because the wires have to move with the mag plate, stranded would be better.  Thoughts?  Does it make any difference?

[seakaye12]

Hi Stewart and Hi to the “Other 16”!

Welcome!    I hope all 16 of you post about what you are working on….and I hope you include pictures!  We love pictures!

Solid wire?  Hmmmm….I’ve never heard that.  I always use the typical 7mm copper stranded wire.  Lets see what others have to say.

Have you come across this resource yet?
http://www.pochefamily.org/outboard/Coils.htm

Chuck

[JACQUES]

solid may eventually break from flexing which is why strand 7mm wire is preferred  and in any event would not cause a problem.

 

Copper is preferred  as a metal because if flexes better .. conductivity wise  well imho any  metallic wire with 0 ohms is 0 ohms .  I have used Belden automotive universal  metalic  wire kits  (never carbon high res.) with boots when it was cheap…. Today  well it is not cheap anymore  !

 

some your local bike or mower shop can sell you a few   feet

Joining AOMCI has priviledges 🙂

[green-thumbs]

Tractor Supply sells ignition wire sets with spark plug boot nolded to end of wire,, If theres is enough roomfor the boot it is cost effective as there are 6 wires with molded goots in set plus some extr wire and etc, The wire does not know if it is on a farm tractor or an outboard. Absolutely correct wire for either application,

Sourcing repair material for old outboard is sometives much easier than you might imagine,

Good Luck

Louis

 

 

 

 

 

 

 

 

 

2

 

[Tubs]

  You want to be very careful with the wiring on this coil as the solder connection at the coil can become loose. There is no available coil that will fit to use as a substitute.   

A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.

[Author]

Posts