1998 Johnson 225 Spark plugs

[fern10]

I have a 225 Johnson 1998 the bottom starboard side Cylinder spark plug always turns dark carbon black. The rest of the spark plugs are fine with an oil gas mixture look. The dark one is dry looking and different. I adjusted the carb associated with that cylinder on the opposite side. made it run a little richer by turning it counter clockwise it started to back fire only on that intake so I turned it back a little. spark plug still getting dark carbon look. Commpression is 90. Any suggestions?

 

[Dhadley]

Re: 1998 Johnson 225 Spark plugs

This works good for me;<br /><br />1- Prime the bulb -<br />2- Turn the key to the "On" position, do not engage the starter -<br />3- Push the key in and count to 8 -<br />4- Turn the key to "Start" to engage the starter.<br /><br />The motor has Quick Start so you should not have to mess with the throttle unless you want to. You may have to hit the primer a couple of time until it warms up. <br /><br />Use fresh 87 octane, good oil and Champion plugs. If the carbs are indeed clean and all else is well with the motor it should start flawlessly.<br /><br />Good luck!

 

[willxuout]

Re: 1998 Johnson 225 Spark plugs

FERN10,<br /><br />I have 1996 Evinrude 225hp v-6 with six carbs and premix my oil at 50:1 with omc oil and add an omc carbon cleaner. The top two plugs (starboard and port) always had alot of carbon buildup after about 3 hours of use. I took it to the mechanic, everthing looks fine (he says), checked the carbs, voltage, ignition, etc. Seven hours later the motor seizes up at WOT . I took the motor to a different mechanic to find out what caused the seizure. We'll see. I would start with rebuilding the carb on the cylinder causing the problem (cheap fix). Then I would make sure that you have good water flow around that cylinder. By the way, do you use the motor in saltwater? Look for any fuel restrictions or air being sucked into the line. Make sure that the appropriate water pump is installed. 20" motors use a different model than 25" motors. SOMETHING IS CAUSING THAT CYLINDER TO BURN HOTTER OR LEANER, FIND OUT WHAT IT IS .

 

[jim dozier]

Re: 1998 Johnson 225 Spark plugs

Pull that plug (the black dry one) while the engine is running and see if it makes any difference. That cylinder may not be firing for any one of several reasons. Check the plug for spark. Try replacing the plug (bad plugs do happend even when new). If you have spark, squirt some premix into that carb throat and see if it picks up any. It odd that you said it backfired when you unscrewed the idle jet to richen it, backfiring is usually indicative of a lean condition. My guess is that you either have a poor spark or a gummed up carb that causes that cylinder to fire less well than the others.<br /><br />You said the compression is 90, what are the other cylinder compressions. Perhaps you need to decarbon the engine, that cylinder may have stuck rings reducing the effectiveness of the combustion.

 

[Dhadley]

Re: 1998 Johnson 225 Spark plugs

fern10 -<br /><br />Thats the second time thats happened -- someone was asking about starting proceedure and I answered. Now it shows up in your posted question. Sorry about that!<br /><br />Dazed and confused!

 

[fern10]

Re: 1998 Johnson 225 Spark plugs

Thanks for the Help! Guys, I Checked this afternoon and ran the engine. I noticed it ran better and did not ramp up and down in RPM's as before. I noticed that the throttle on that cylinder was open ever so slightly compared to the others that were completely closed. I adjusted the Allen screw that tightens that throttle. The valve is closed like the others. I tapped it in place and now it idles at about 2500 RPM's out of the water. If to much air is going into the cylinder could this be why the Spark plug gets carbon black. If I change the plug and it still get's black what then. The other 5 cylinders are fine with new plugs. Compression on other cylinders within 15%

 

[Dhadley]

Re: 1998 Johnson 225 Spark plugs

On compression you are looking for a difference of no more than 15 lbs. 2500 rpm out of the water may be a tad high. Once you put it in the water (to get backpressure on the exhaust) you can set the idle.<br /><br />If that plug is getting "sooty" looking then yes it is pulling air from somewhere. A common place for an air leak is on those side plates on the carb. <br /><br />Good luck!

 

[fern10]

Re: 1998 Johnson 225 Spark plugs

Thanks Dhadley ,<br />I will try putting in a new plug and test for a good spark. I think I have enough fuel going in. Now that the carb throttle valve is fully closed I will watch that plug.