Muncie 1B39 spark plug type

[Frank Cornine]

I just recently joined the AOMCI and was thrilled to find that this forum exists. I have acquired several vintage outboards that require work and was hoping to obtain advice and information from members. One unit that I started working on is a Muncie 1B39. The spark plug that came with this unit was a Firestone F-80-F. The plug seems rather long in length as the terminal end with the plug wire attached comes very close to the interior surface of the side cover. So close it looks like it could short the ignition out. I have no documentation with this outboard so I figured I would ask the experts for advice.

Thanks,

Frank

[Buccaneer]

I can’t find a spark plug chart showing what plug your 1.2 hp Muncie Junior,
single cylinder is suppose to take.
Is it a 14 mm or 18 mm plug?

Just found this plug on the net showing it’s 14 mm. Not sure what to think about
the “Radioactive” deal, lol.

Firestone F-80 Polonium Radioactive 13/16″ Hex Electrodes Spark Plug 14MM

I would think that 1/4″ gap between the end of the spark plug and anything metal would
be absolute minimum.
Maybe someone will have a chart showing alternative plugs.

Prepare to be boarded!

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Frank Cornine

[HARRY D. NICHOLSON]

My 1961 Champion chart lists a Champion J8J (same as J8C) for a Neptune 1A39 (1.5HP) which should be the same motor as model 1B39.  Oil mix shows 1 pint per gal gas, plug gap .025

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Frank Cornine

[Frank Cornine]

Buccaneer and Harry,

Thanks for the quick reply’s! I believe the Firestone plug is 14mm. I’ll pick up a Champion J8J plug and give it a shot. I was hoping to find a shorter, compatible plug that would provide more space between the terminal and the side cowl. But I’ll try the Champion. I can’t wait to get this Muncie back together and fire it up.

Thanks again……

[HARRY D. NICHOLSON]

They do make some plugs in a short version.

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Frank Cornine

[Tubs]

Here are some short plugs you could check out.
I use the J-17-LM in several motors where I
need a short plug. Mostly small motors with
covers like Scout’s & Mate’s but I also have
a pair in a Martin 75 TS my son-in-law uses
for fishing. They have been in it about 4 or 5
years now. They seem to be a good heat range
for the motors I have used them in but there
are others to choose from.
Tubs.

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

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Frank Cornine

[Frank Cornine]

Thanks Harry,

I had thought about looking for a shorter plug. Tub’s also replied and provided some alternative plugs that would work. Thanks to Tub’s also……

[HARRY D. NICHOLSON]

A more cost effective way may be to use a good rubber ‘sparky’ cover on the plug if it fits.

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Frank Cornine

[Author]

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