Spark Plugs

[Lakesailor]

I've had a missfire on my Johnson 70 VRO.
"Ah ha!" you all say, "told you you can't run a motor like that at 10 knots."

But no. It's running NGK plugs. Research shows that the US forums all express the opinion that only the Champion QL77JC4 plugs will run cleanly in this (and other) Johnson motor.
Johnson say that if you don't use this plug you will get a gradual ignition deterioration to a missfire which you can't get rid of.
The theory is that Johnson and Champion worked on the motors together and the "Q" part of the plug notation is the radio suppression element.
Although other manufacturers give equivalents, Johnson claim the suspression is not the same and effects the ignition circuit.
Johnson do not recognise there is any equivalent to the QL77JC4.

Now this all sounds very cosy between Johnson and Champion, except after trying several dealers I spoke to Mike at South Coast Marine and he, whilst admitting he didn't know why, said I'll never get it to run cleanly without using Champion plugs.

This is the route I'm using and have now got some to install.

What do forumites think? Does the explanation hold water?

I will report back on the clean running situation (and it's not that bad at the moment on NGKs) but I'd like your views before I reveal the results.

 

[JKay]

better people than me will expain why But with 2 strokes the

plug that works best works best

Mr Kwaker/unit18 will know!

cheers Joe

 

[SvenglishTommy]

In my experience with plugs, which is mostly with cars not outboards, I have come across the same kind of situation. People seem to lean toward NGKs as the best plugs, and I have always used them in the past. However, I have noticed my car doesn't seem to run as well after replacing the original Bosch plugs with NGKs.

One of the NGK codes after the heat range on the plug designates that it is a 'special' plug, which I assume means it is designed specifically as an aftermarket version of a competitors specialist plug. I'm not 100% convinced that it isn't just buddying up, but it may hold some water.

I'd be interested in your findings.

 

[toad]

I have used NGK plugs for 30 years without one failing but I have heard that some French cars are giving problems unless run on Bosch plugs.

 

[ccscott49]

My triumph motorcycle only likes NGK plugs, all others (equivs) just dont give the same performance, dunno why, but seen it many times before.

 

[JKay]

Snap /forums/images/graemlins/cool.gif

cheers Joe

 

[Lakesailor]

Well although you are pleading for NGK that may actually re-inforce the case for Champion in Johnson/Evinrudes.
It seems that some manufacturers and plug makers work hand-in-hand to produce a combination that works.
I have a Honda CRV and it seems that they only run well with Honda spark plugs.

I am fitting them tommorow morning and probably will find it runs beautifully. Of course the test is how do they run 10 - 20 - 30 hours later.

 

[bdsweeting]

Have a look here at the Champion site, they explain the reasons for the Q plug and certain Outboard motors.

http://www.championsparkplugs.com/results_cross.asp?pid=QL77JC4+&x=53&y=14

 

[JKay]

Mr Phil(of MBM fame)

I never pushed NGK

I suggested the right plug for the right engine

cheers Joe

 

[Lakesailor]

Ahh. Took a bit of finding but that backs up what I discovered on the US forums[ QUOTE ]
Outboard marine Capacitive Discharge Ignition (CDI) such as used on some Johnson and Evinrude marine engines require a special inductive type resistor (such as a Champion Q-type resistor). Use of non-inductive resistor type plugs on these motors can cause misfire and poor performance.

[/ QUOTE ]

So that's why the NGK equivalent, isn't. If you get my drift.

 

[bilbobaggins]

Shameless, unabashed, undiluted geekery!

Getalife!

Getaboat!


/forums/images/graemlins/grin.gif

 

[Lakesailor]

Get Knotted!












I was a petrol-head for many years. It's in the blood.

 

[Lakesailor]

Yes. I wasn't saying NGK aren't great in some applications. But it seems that they haven't really provided an equivalent in this particular case.

(fame. I don't think so)

 

[macd]

More often than not it's impossible to know whether entreaties to use "oil X" or "washing powder Y" are based on anything but the cosiness you suspect. But it is quite possible that Johnson and Champion actually collaborated in the development of the engine and its ignition, just as motorcycle manufacturers will often work with a particular tyre company when developing a bike. So it could well be that the anecdotal evidence cited is based on fact.
With bikes, incidentally, it's well known that certain engines just won't work well with certain plugs and even oils to supposedly the same spec.

 

[reginaldon]

Re: Spark Plugs - Yamaha 5

I have had increasing problems in starting my Yamaha 5 2stroke to the point that now I can't get it started, plug problem? Once started it ran fine.
I'm getting long in the tooth and don't fancy a long carry from my mud (dy) berth - any help appreciated.

 

[SvenglishTommy]

[ QUOTE ]
... I have heard that some French cars are giving problems unless run on Bosch plugs.

[/ QUOTE ]
Interesting. My car is indeed French.

 

[Lakesailor]

Re: Spark Plugs - Yamaha 5

At £4 each it's worth a crack. Mind you this has been a specific Johnson/Evinrude issue.
Could be worth trawling the iboats forum for an answer. Mind you there are 300 pages on Yam/Suzuki

 

[andyball]

Re: Spark Plugs - Yamaha 5

cdi ignitions were very common on small to medium motorcycles & likely still are... some charge the capacitor via a coil winding, others via a 12V supply ( cdi more often refers to the former ).

none of them, to my knowledge, had any issues with run of the mill ngk plugs, except when engine/ignition spec'd a wide gap or fancy plug-type ( eg surface gap )

In an older engine - the caps, if resistor type especially, can be a problem. The soft rubber ngk racing ones are best imo, if they fit.


sounds like champion/johnson rustled up some with inductors rather than resistors, after maybe some issues with the resistor breaking down with the high voltage ( seems a bit unlikely tho, but possible ). with some cdi's, an open circuit can wreck the black box.


praps break out yr mutlimeter & see what resistance the special champions have from terminal to electrode - if lower than usual 5K +, is likely an inductor of some kind.

 

[Lakesailor]

Re: Spark Plugs - Yamaha 5

Yup go back a few posts and you'll see [ QUOTE ]
require a special inductive type resistor (such as a Champion Q-type resistor)

[/ QUOTE ]

I tried it on a multimeter and it read 12 (or is that 120 as it was on the X10 setting) Ohms. On the X1K setting it reads 0.1.

 

[andyball]

Re: Spark Plugs - Yamaha 5

yes indeed, no suppression to speak of from the resistive part of that - just an inductor.

This would have the effect of slowing down any sudden rise in current, ie, when the plug sparks. The coil secondary winding does this too, but usu wound to limit the effect as far as poss.