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Author Topic:   Spark plugs
bmclernon posted 04-24-2002 08:57 AM ET (US)   Profile for bmclernon   Send Email to bmclernon  
I have a 1976 85 HP Johnson on the stern of my 1976 Montauk. The owners manual calls for L77JC4 plugs. Just receintly my mechanic installed QL77JC4 plugs. When I asked him about the difference He was evasive - mentioned resistor, longer lasting etc. Does any body have the good skinny on this matter?
Chap posted 04-24-2002 09:51 AM ET (US)     Profile for Chap  Send Email to Chap     
I asked that question once myself and was told that the Q designation stood for a suppressor style plug. Neither of us knew what that indicated and I never pursued it. I went with the recommended Q plug and the motors run fine.
Someone else, I'm sure, knows more about this mysterious "Q."
whalernut posted 04-24-2002 07:39 PM ET (US)     Profile for whalernut  Send Email to whalernut     
I have a 1975 85 h.p. Johnson, and the "Q" is for Resister for the electronics to work properly without interference for electric feilds, so either are fine, but the "Q" ones are better if you have electronis such as a VHF and fishfinder, did you notice the Resister models are at least a buck for a peice, that is because they have that resister quality in them. I have found my Johnson likes Denso brand plugs the best, it won`t troll very long on Champions, but with Denso`s it will troll along time and not stall and foul. Jack.
whalernut posted 04-24-2002 07:43 PM ET (US)     Profile for whalernut  Send Email to whalernut     
I meant to say: the resister plugs are at least a dollar more a peice. Jack.
gunnelgrabber posted 04-24-2002 09:11 PM ET (US)     Profile for gunnelgrabber  Send Email to gunnelgrabber     
would you put the complete denso # on so i can be specific when i go hunting some? you've convinced me to try them.... thanks...lm
whalernut posted 04-24-2002 09:40 PM ET (US)     Profile for whalernut  Send Email to whalernut     
Hi, my boat is still in storage, and it is like 130 miles from me, but when I get it out, I will surely let you know. I use the Non-Resister models and I only pay like $149 for them!!! They run awsome!!! I buy them in Conneaut,OH. at Auto Zone if that helps any, do you have Auto Zone near you??? Maybee give them a ring. I remember when they swithed from selling Champion to Denso a couple of years ago and I was hesitant to try those Densos, but man did they prove me wrong and I am very happy with them, I run 89 Octane Marine Fuel in my boat. Jack.
jimh posted 04-24-2002 11:42 PM ET (US)     Profile for jimh  Send Email to jimh     
Resistor plugs are used to suppress generation of radio frequency energy by the sparking of the ignition system. Virtually all automobile engines use resistor plugs so to reduce interference with the car's radio.

The same reason applies to boats. If you have a radio or other radio-frequency receiving equipment (like a fish finder or depth sounder), the sparking of your engine's ignition can create interference. Using plugs with resistor elements in them reduces this.

It also reduces (slightly) the spark. Usually the slight difference in spark is not a signficant as the much larger improvement in radio operation.

Incidently, the initial transmission of radio were generated by using spark-gap techniques. The famous sending of a message across the Atlantic from Table Head at Glace Bay, Nova Scotia to Poldhu, Scotland was accompished with a spark gap transmitter. That should be an indication of the power and ability of a simple spark gap to create radio frequency energy.

Later, improved techniques of generating radio freqeuncy energy became known as "continuous waves", which was often abbreviated "CW". The term CW came to be equated with radio-telegraphy, or "Morse code" transmission. This is also the double entendre of this website's domain name.

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