96 Johnson 112 SPL fouling plugs

[StriperChaser]

I did a search and read all the past topics about oil fouled plugs. Seems there's many things that can cause the problem, wrong plugs, low grade oil/gas, thermostat, bad coil, etc. I have just assumed I had accumulated a tank of old fuel with too much 2 cycle oil. I have to mix my oil (no VRO), have a 40 gal tank with a fuel gauge that has never worked correctly, and have never let the tank get much below half empty. I mix the oil to gas ratio (50:1) but tend to add more oil than needed rather than not enough after filling the tank. Everytime I take the boat out I just top off the tank with somewhere between 6 to 12 gallons of fuel. I haven't started trolling yet this year but need to resolve this problem before I start. I've decided to siphon the tank and start fresh with new gas, oil and plugs. Do you think that is just too simple of a fix? I wonder after reading all the other posts. Just seems that years of never emptying the 40 gal tank would lead to a bad batch of fuel sooner or later. Any suggestions?

 

[Dhadley]

Re: 96 Johnson 112 SPL fouling plugs

You may be totally amazed how bad 30 day old fuel will run. Fresh 87 octane and new Champion plugs may be just what you need.<br /><br />Good luck!

 

[seahorse5]

Re: 96 Johnson 112 SPL fouling plugs

Are you using the Champion QL82C plugs gapped at .030" as recommended by the factory?<br /><br />What temperature are the heads at after idling for about 5 minutes?

 

[StriperChaser]

Re: 96 Johnson 112 SPL fouling plugs

I am using Champion QL82C plugs gapped at .030" and have also tried Autolite, but not sure about the head temp. The last new plugs fouled just a few trips after installation, all oil fouled. What's the best way to check the head temp and what temp should it be?

 

[seahorse5]

Re: 96 Johnson 112 SPL fouling plugs

The best way is to use an infrared temp gun for a direct reading, around 140 degrees. A quick way is to hold 2 fingers on top of each head after idling a while. If you can hold them against the head for more than 2 seconds, the motor is not warming up enough.<br /><br />When you say they foul, do they quit sparking and the motor stops, or is it only one or two plugs? How about a bit of the motor history and what's been done to it.

 

[StriperChaser]

Re: 96 Johnson 112 SPL fouling plugs

In reply to Seahorse, the wiring harness was replaced by the dealer in the fall after a no start problem with no spark at the plugs. They never determined which wire was bad but it started and ran great afterwards. Trying to resolve the no start prpblem, I had replaced the plugs before taking it to the dealer. After only a few trips to the lake it oil fouled the plugs and would hardly get on plane. I replaced the plugs again wanting to just start with good new plugs. With new plugs, it ran great, but again after several trips to the lake, the oil build up on the plugs caused hard starts and loss of power. I have cleaned the current plugs and checked the gap two or three times since the fall. I'll check the heat off the heads, but still plan to siphon the fuel. I'm thinking it's kind of like a small 2 cycle (chain saw / weed eater), where old fuel can make a big difference in performance. With the 40 gals of fuel and most never being used, it just seems like the most logical place to begin. All suggestions are appreciated.

 

[seahorse5]

Re: 96 Johnson 112 SPL fouling plugs

Those motors will run well over 100 hours on the same plugs, both trolling and cruising. You either have carb problems with flooding or weak ignition that is breaking down after you run it a while. Since it won't get on plane, you are losing one or two cylinders. Find out which ones to narrow down the problem.

 

[Down South]

Re: 96 Johnson 112 SPL fouling plugs

Hi StriperChaser,<br />I have a 96 model 88 SPL on a boat with the built in tank too. Your problem may be in your oil mixture. (Too much) What I do is, I have several six gallon gas cans. I add the right amount of oil to each can then put exactly six gallons of gas in each one of them. When I need more gas I use one of my premixed gas cans to fill it up with. This way I always know my gas and oil is mixed right. Make sure you use a good grade of outboard motor oil too.