See full version: Champion or ngk spark plugs
NGK plugs have bad reputation when used in Johnson and Evinrude outboards which I suspect is not because there is anything wrong with NGK plugs, au contraire, but because in the absence of inductively suppressed NGK plugs until relatively recently, resistor plugs were recommended and used with sometimes disappointing results.
Re: champion or ngk spark plugs more
I apologise for not prevously stating the source of the article.
A full technical explanation of the need for inductive suppression rather than resistive suppression can be found at http://members.iinet.net.au/
The hard line approach would be to respond to all questions about plugs by saying use only the engine manufacturers recommended plugs! In the case in point this amounts to QL77JC4 or QL78YC.
I prefer the softer approach, particularly with questions originating in the UK where Champion plugs are not so readily available, namely to suggest the nearest equivalent NGK plug. In this case BZ7HS-10.
BR7HS is NOT equivalent to QL77JC4 no matter what your dealer may try to tell you.
Let us know what you find. [links]
Spark Plug and compression
The engine model number you state of J140TLATF, I believe to be incorrect. It should be J140TLETF. There is no "A" in the model number! more
The standard recommended spark plug is the Champion spark plug QL77JC4, gaped at .030.
With all s/plugs removed. check the compression and spark. The compression should be around 100 psi and even on all cylinders. the spark should jump a 7/16" gap with a strong blue lightning like flame. a real SNAP. [links]
The alternative spark plug is the surface gap plug QL16V.
The OIS 2000 ignition has to have the power coil supplying power in order to operate the QuickStart, S.L.O.W., rev limiter, and fire the coils beyond cranking speed. The optical sensor located on the top is fed power from the power pack and sends crankshaft position, cylinder location and direction of rotation back to the power pack. here
Check the sensor eyes for dirt, grease and the like. If you need to clean it, use denatured alcohol and a Q-tip. Do not use any other cleaning agent because damage to the optical lens will occur.
Low readings on all checks indicate a possible problem with the flywheel magnets that needs to be checked. [links]
How to Check the Spark Plugs here
Thirty years ago when an engine refused to start, a cranky ignition was likely the cause. Today with electronic ignition systems, it is fairly easy to troubleshoot a startup problem and should the spark plugs prove to be the culprit, a quick fix. If your engine is missing, mis-firing, or just will not start, follow these steps to troubleshoot. This way you’ll know if the issue is minor or requires more investigation by a skilled marine technician.
To troubleshoot the ignition system, start with the spark plugs. Use a spark plug socket, ratchet and extension to test the plugs. To begin, remove just one plug. Inspect the plug tip and notice if it is soaked with oil or fuel. If wet, this indicates a fuel line issue. If dry, note the color and condition of the plug tip. Tips that are blistered or melted mean the wrong plug has been used. Check your owner’s manual to determine the right plug for your Johnson outboard ignition system, simply give us a call, and we’ll be glad to assist. [links]
Here is an engine overview. For Johnson outboard ignition systems to run, the requirements are compression, fuel and spark. Sound motor function is determined by compression, the air/gas/pressure induced explosion that occurs in the pistons must be sufficient to turn the propeller. For this to work the fuel lines must not be clogged and the fuel injectors or carburetors are fully-functional. Spark from the spark plugs provides the catalyst that produces engine power.
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