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Author Topic:   Reading Spark Plug Color

jimh posted 10-04-2006 10:31 PM ET (US)
In the third season of owning my 1992 Evinrude V6 225-HP outboard, I finally feel like I have the motor running in tip-top condition. I have worked out several problems, and the old looper seems like it is cranking out like it should be. So last week I had a chance to run her at high speed for an extended run, about three or four miles. I cut back to idle and quickly came to my dock. I let the engine cool off, then I pulled the cowling. I removed the spark plugs, and checked the color of the insulator below the center electrode. At last, I had achieved the elusive tan color!
Previously, every time I had checked the plugs they were wet and oily, and the insulator color was nothing but black. Now, the plugs were relatively dry and the insulator was a nice tan color. The plugs were almost identical, except cylinder #6's plug was a little darker brown, and a touch wetter than the rest.
It had been a while since I installed these plugs, probably about 30 hours or more of running time. The gap had grown from the 0.030-inch I set them to. I re-gapped the plugs and put them back in. I was going to yank them out later in the week, but we were having so much fun riding around in the boat I never got to it.
The biggest change recently in the ignition system was a new Power Pack. The old one was giving me fits with intermittent spark to cylinder #5, and I finally replaced it. It looks like as a bonus I am getting better firing on all the plugs. They sure looked nice with those dry, tan insulators.
See more about the power pack replacement dilemma in http://continuouswave.com/ubb/Forum3/HTML/011635.html.
I had read about interpreting the spark plug insulator color as an indicator of how well the engine is running, but until now I had not been able to achieve the desired light brown or tan insulator color. With the engine running better than ever, I was delighted to find my spark plug center electrode insulators were finally the proper color, too.
jimh posted 10-04-2006 10:43 PM ET (US)
Here is the motor, running along at 40-MPH:
http://continuouswave.com/whaler/movies/evinrude225WhalerWattsBarLake. MOV
The Judge posted 10-05-2006 02:29 PM ET (US)
At least now your gas tank is empty for winter storage after that 4 mile WOT jaunt. Think of all the $$ you will save on gas additives.

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Author	Topic: Reading Spark Plug Color
jimh	posted 10-04-2006 10:31 PM ET (US) In the third season of owning my 1992 Evinrude V6 225-HP outboard, I finally feel like I have the motor running in tip-top condition. I have worked out several problems, and the old looper seems like it is cranking out like it should be. So last week I had a chance to run her at high speed for an extended run, about three or four miles. I cut back to idle and quickly came to my dock. I let the engine cool off, then I pulled the cowling. I removed the spark plugs, and checked the color of the insulator below the center electrode. At last, I had achieved the elusive tan color! Previously, every time I had checked the plugs they were wet and oily, and the insulator color was nothing but black. Now, the plugs were relatively dry and the insulator was a nice tan color. The plugs were almost identical, except cylinder #6's plug was a little darker brown, and a touch wetter than the rest. It had been a while since I installed these plugs, probably about 30 hours or more of running time. The gap had grown from the 0.030-inch I set them to. I re-gapped the plugs and put them back in. I was going to yank them out later in the week, but we were having so much fun riding around in the boat I never got to it. The biggest change recently in the ignition system was a new Power Pack. The old one was giving me fits with intermittent spark to cylinder #5, and I finally replaced it. It looks like as a bonus I am getting better firing on all the plugs. They sure looked nice with those dry, tan insulators. See more about the power pack replacement dilemma in http://continuouswave.com/ubb/Forum3/HTML/011635.html. I had read about interpreting the spark plug insulator color as an indicator of how well the engine is running, but until now I had not been able to achieve the desired light brown or tan insulator color. With the engine running better than ever, I was delighted to find my spark plug center electrode insulators were finally the proper color, too.
jimh	posted 10-04-2006 10:43 PM ET (US) Here is the motor, running along at 40-MPH: http://continuouswave.com/whaler/movies/evinrude225WhalerWattsBarLake. MOV
The Judge	posted 10-05-2006 02:29 PM ET (US) At least now your gas tank is empty for winter storage after that 4 mile WOT jaunt. Think of all the $$ you will save on gas additives.