fouling plugs

[71whaler]

I think I am having a problem with fouling plugs on my 1983 75HP Evinrude. Went out one day and the boat bogged and wouldn't go over 5 knots. Changed the plugs, they looked oily, and changed the water/fuel seperator. Boat ran great. Next day went to go fishing and again, it was bogging down and was idling rough. I have both a Seloc and OMC service manual. They mention fouled plugs being caused by too rich of a mixture but not how to correct it. <br /><br />The carbs were completely dissembled and cleaned last year and the boat ran great all year. It was winterized in January and I brought it out of storage in May and did two trips before this bogging problem started. <br /><br />Any thoughts?

 

[CATransplant]

Re: fouling plugs

What plugs are you using?

 

[71whaler]

Re: fouling plugs

Champion QL77JC (I think that was the part #) These are the ones recommended by the parts store for this model. Gap at 0.03

 

[Solittle]

Re: fouling plugs

Try 0.040.

 

[71whaler]

Re: fouling plugs

I will try that with a new set of plugs. However after bringing the boat out of winter storage I installed new plugs and gapped them at 0.040. The first two trips out the boat ran well and then the problem started on the third trip. When removed the plugs looked like they had black oil on them. I can try and post a picture if that helps.

 

[71whaler]

Re: fouling plugs

The more I think about this problem, the more I think it is some kind of ignition problem as when the motor boggs down it does not help to tap the choke. So this would indicate the carbs are not the problem, correct? What is the best way to test whether I am getting spark at each plug? I remember people mentioning holding the plug wire close to the block at night, anyone have any detailed instructions on this? I also heard mention of a spark tester.

 

[csheps]

Re: fouling plugs

simple way to test for spark at plug is to remove plug and connect ht lead, rest it on cylinder block, and turn it over. aspark should jump the gap at electrode, if its tested in day light and you are man enough,hold the plug in your hand.you will soon know if its working!!

 

[71whaler]

Re: fouling plugs

Thanks. I don't know about holding the plug in my hand....but for the other method, you just pull the plug wire and rest it against the block, remove the plug itself and then turn the engine over?

 

[Basscat 1]

Re: fouling plugs

Or, clamp it to the block with a pair of vise grips. Just keep over to the side away from the plug hole.

 

[71whaler]

Re: fouling plugs

OK, I checked the plugs and sure enough the top cylinder is not firing. When the engine is idling and I pull the top wire there is no change in idle, however when I pull the middle and bottom wires there is a very noticeble change in idle. So next I swapped the plug wires between the middle and top clylinders and still the top does not fire. So I am thinking the ignition coil (square black box that the wire runs to) is bad?? Looks pretty straight forward to replace. Should I replace all three while I am at it? <br /><br />Lastly, I checked the compression and here are the readings I got, <br /><br />Top cylinder 137psi<br />middle 120psi<br />bottom 130psi<br /><br />Should I be concerned?

 

[R.Johnson]

Re: fouling plugs

Testing for spark by grounding the plug to see if you have spark across the electrode is no test at all. That engine should jump about a 3/8 inch gap with a strong blue spark. On most any outboard engine, if you pull the plug after the engine has been run at idle for any time at all, the plug will appear wet. This is normal. If the engine runs normal for a short time, then breaks down after warm-up, that suggest's an ignition problem. On your engine you have the ign. sensor's, charge coil, power pak, and three coil's. You have to test each component to isolate this problem. The problem being, this is best done with a peak reading volt meter, and a proper spark checker. Trying to out guess the problem can get exspensive. In this case, I would really advise pulling the head, and taking a look at that #2 cylinder.

 

[71whaler]

Re: fouling plugs

Someone else mentioned fixing the ignition problem and then doing a decarb with seafoam and then rechecking the compression. I have been going through my manual and I am going to try the tests to fix the ignition problem. Does this sound reasonable or should I go ahead and pull the head? I've never done this before.

 

[71whaler]

Re: fouling plugs

Another question, I have been searching previous posts about compression and noticed that some say a difference between 10% is OK while others say a difference of 15% is OK. Which is it? Seloc manual says difference of 5psi bad.

 

[Basscat 1]

Re: fouling plugs

You can clamp the plug with vise grips at about a 3/8 gap from the electrode to the engine block. The spark plug tester is the best method, but not everybody has access to buying or borrowing one.<br />Dont pull the cylinder head until you do a decarb.

 

[Solittle]

Re: fouling plugs

I don't know your motor but the first thing that I would do is to swap the plug, wire & coil from the dead cyl to one of the others. If the problem follows you have isolated it to one of those three parts. Repeat until you have it down to one & replace.

 

[71whaler]

Re: fouling plugs

Thanks guys. I'll let you know how I make out.