Eismann coils

[green-thumbs]

Not to diverge from capacitor /condenser discussion, but, back to spark
plugs. I believe the reason so many KD and WD model outboards are
missing their spark plug covers is that the original spark plugs were shorter than standard spark plugs (and likely more expensive) so when
it came time to replace owners used the standard length lower price
spark plugs. The spark plug covers could not fit over the longer spark
plugs so were left off and lost. There has been some discussion in
past of using the compact spark plug which has a “C” prefix. such as
CJ 6 C if I recall rightly.
Louis

t

[Buccaneer]

Louis, I put the original J8J plugs back in for the time being. They definitely
are shorter than the modern J8C plugs. I’m assuming that the CJ6C are
a “colder” plug, which probably would not matter for the little I’ll run the motor.
There are J8J plugs for sale on EBay. Was there “short and long” J8J
plugs back in the day, or were they all shorter? None of the sellers give
the length, but I suppose I could inquire.
Thanks!

Prepare to be boarded!

[fifty20ne]

Guys please take a look at Mercury Master Spec Chart?
KD-4 shows Champion J7-J spark plug, J8-J for singles.

Anyway here is a pic of four different spark plugs side to side.

AC 45M, Champion J8-J “Per Box” NOS (Phos Plated), Champion J8 (Zinc Plated), Champion J8-C (Zinc Plated)

The AC 45 M is actually shorter than old style J8-J

Looks like the post war (Zinc Plated) Champion J8-J or J8 will work, but must have removable tip (Red & White Packaging) Not Blue & White (Fixed) solid “Non- removable tip”!

I also find you have to use a smaller diameter brass nut for proper clearance!

• This reply was modified 4 years, 3 months ago by fifty20ne.
• This reply was modified 4 years, 3 months ago by fifty20ne.

[billw]

In my recent work on a WD3S,(basically the same as a Merc KD3) I used a CJ8 spark plug. Not only did the engine run just fine with it, you can even fit a rubber spark plug boot under the aluminum plug cover!

Long live American manufacturing!

• This reply was modified 4 years, 3 months ago by billw.

[Buccaneer]

Good to know of the other options! I must have looked cross wise when I
looked up the plugs for the KD4 as J8J, instead of J7J. Of course, the
cross reference for J7J list the J8C, which would be too long.
I like the idea of the CJ8 plugs using the Sparky boots!
Thanks.

Prepare to be boarded!

[The Boat House]

[Buccaneer]

Thanks Tubs, at least the J17LM are readily available…. I think!

Prepare to be boarded!

[The Boat House]

• This reply was modified 4 years, 3 months ago by The Boat House.
• This reply was modified 4 years, 3 months ago by The Boat House.
• This reply was modified 3 years, 2 months ago by The Boat House.

[labrador-guy]

Good to know about those J17LM plugs. I have a Zephyr that’s gonna get a set of them. New wires and shorty plugs maybe it will help that spark jumping and fire making problems that plagues those motors.

dale

[Author]

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