There is a short Champion J8 available but its hard to locate.
I have given my 75 TS to my son in law to use for fly fishing.
He fly’s to one end of the lake and fishes for 5 minuets and
the fly’s to another end. I use these in my motors that need a
short plug. The LM is for lawn mower so I can find them at
home centers as well as hardware stores if I need one
although I have never had a failure. These have been in the
Martin for 3 years. I put them back in.
Tubs.
A "Boathouse Repair" is one that done without having tools or the skills to do it properly.
Tubs, Yes, that Champion plug is available , the problem is that it does not have a screw thread terminal that you need for applications which yse ring terminal spark plug wires. Like on the Zephyrs, I don’t recall the wire termination on Martins.
The 456 number in the chart above cross references to
J19LM or RJ17LM Champion plugs.
If the later is a “resistor” plug, I guess I’d opt for the other.