Spark Plug Question

My manual reccomends changing sparkplugs every year. I do this. I am just curious what the reasoning is. Cars specify a certain number of Kilometers to replace them.
When I do replace them they look almost new. I will continue to raplace them yearly. It just seems weird throwing out perfectly good plugs. I keep one of the old sets on my boat for spares(just in case).

Another question. My motor is a 2004 Johnson 50HP 2-stroke. Johnson reccomends Champion QL78YC plugs. Now with cars you can usually find several equivelant plugs from different manufactures. You can upgrade to platnum etc.

Is there equivelant plugs from different manufactures or upgraded plugs? Or am I limited to the plug they reccomend.

The plugs they reccomend work fine. I am just curious if other companies make plugs for this motor or if Champion offers other models?

Thanks in advance,
Jay

Re: Spark Plug Question

Your motor was designed around the heat range provided by the specified Champion plug. Yes -- every manufacturer has a "cross-reference" to their plug from some other manufacturer. The only problem is the "other manufacturers" plug may not be "exactly" the same heat range as the Champion. As for platinum, surface gap, and other exotic plugs you would be wasting your money unless you have some very specific operating condition were a special plug might improve performance in that situation. As inexpensive as plugs are, why not change them every year. It at least gives you an opportunity to do a visual check on engine health. Yes -- you can tell if something is amiss by the color of the plug. Black & oily is due to extensive idling/trolling. Cream to light tan is perfect. White may be indication of water intrusion or very lean condition. Melted electrodes or pitting is a sign something is seriously wrong and needs attention now as detonation or overheating may be happening. New plugs will be white for a short time after they were installed. Just use the plug that's recommended.

Re: Spark Plug Question

Thanks Silvertip,

Great advice, never thought of using the plugs as a visual check on the health of the motor, will do.

Plugs are cheap and I only need 2 of them. I will continue to replace them every year.

Re: Spark Plug Question

"I will continue to raplace them yearly. It just seems weird throwing out perfectly good plugs. I keep one of the old sets on my boat for spares(just in case)."

Waste in my opinion is right... if they look fine when ya pull them, use them until one gives out, which in a good running motor, will probably be a job for one of your grandchildren down the line

Re: Spark Plug Question

Scaaty, thats what we did with my Dad's 15HP Yamaha. Just kept reusing them and kept a spare set on the boat.

I don't ever remember changing them and it started and ran perfectly for years.

Re: Spark Plug Question

Certain motors seem like they NEVER need a new plug. Others seem to foul out a little too often.(i got one). Too many variables, but checking them mid season always a good idea. A good plug read can say more about an engines health than anything else. Like always, carry a spare set.

Re: Spark Plug Question

If the colour is good and the motor is running fine then a quick clean, check the gaps and put them back but as stated above always carry spares with you (and do not forget the wrench)

Re: Spark Plug Question

I had my tower (115 I6) for 7 years. Changed them the first year and thought that was stupid as mentioned. Never changed them again; didn't need to. Engine purred at 6 grand at WOT which is where it ran if it wasn't in the "no wake" zone. d......and that's before I heard about decarbing and Sea Foam.

Mark