1993 15hp Johnson - removing plug wires while running question?

[johnsland8]

While running my motor today, it was running a little rougher than I like. I removed each of the plug wires in turn while running. When I removed the top plug wire I noticed no obvious difference in the way it was running, but I did get shocked when I touched it so it was getting juice. I replaced it and removed the bottom plug wire and the motor would die instantly. I did this twice.
Does this mean anything to me?

Thanks!

 

[johnsland8]

Re: 1993 15hp Johnson - removing plug wires while running question?

I guess that wasn't the best described question...

I assume this means it's not firing on the top cylinder, only the bottom. But what would cause this besides a bad plug? Like I said, it was getting spark thru the wire, I could feel it. I did a compression check also, I got 125 psi in both cylinders.

Any ideas?

Thanks again.

 

[Joe Reeves]

Re: 1993 15hp Johnson - removing plug wires while running question?

Yes, the engine is not firing on the top cylinder.

Compression of 125 psi is excellent.

With spark plugs removed, check the spark which should jump a 7/16" gap on that engine with a strong blue lightning like flame..... a real SNAP! Does it?

Let us know what you find.

 

[johnsland8]

Re: 1993 15hp Johnson - removing plug wires while running question?

Yes, the engine is not firing on the top cylinder.

Compression of 125 psi is excellent.

With spark plugs removed, check the spark which should jump a 7/16" gap on that engine with a strong blue lightning like flame..... a real SNAP! Does it?

Let us know what you find.

Yes it does do that.

 

[Rick.]

Re: 1993 15hp Johnson - removing plug wires while running question?

Hopefully you just have a bad plug. Try switching the plug locations and see if the problem follows the original top plug. Rick.

 

[johnsland8]

Re: 1993 15hp Johnson - removing plug wires while running question?

Hopefully you just have a bad plug. Try switching the plug locations and see if the problem follows the original top plug. Rick.

But if the plug is sparking like that, wouldn't that mean it was good?

 

[R.Johnson]

Re: 1993 15hp Johnson - removing plug wires while running question?

You could feel it fire, take off your shoe's, stand in wet grass. it will sometimes feel stronger if you do this. If it will fire the engine , it will realllly feel strong. Quite a spark test,

 

[johnsland8]

Re: 1993 15hp Johnson - removing plug wires while running question?

You could feel it fire, take off your shoe's, stand in wet grass. it will sometimes feel stronger if you do this. If it will fire the engine , it will realllly feel strong. Quite a spark test,

I'm not sure what you are talking about? I'm sure that was supposed to be funny!

But just to be clear, I pulled the plug from the motor, placed it back into the plug wire, and then checked the spark against a bolt head.

It was a strong blue spark that snapped/popped very strongly across about a 7/16" gap, like suggested. I then compared it to the known good one, and they were essentially identical.

How better can I test it? I am eager to learn?

 

[Rick.]

Re: 1993 15hp Johnson - removing plug wires while running question?

You can buy a spark tester which basically has an adjustable gap that you can set to 1/2 inch or any other measurement. It connects to your pug wire and ground and you can watch the spark jump the gap and see its condition. For darn sure R Johnson is kidding. Don't try that method. Lord knows we all get shocked enough working on these motors as it is. If I'm being misunderstood let me try again. It makes no difference how good your spark is if you have a bad plug. I'm suggesting you may find your top plug is shot. Plugs can fail under compression and yet appear to work holding them close to a ground source. That is why I suggest moving it to the lower cylinder to see if it fails on that cylinder or if in fact it works. Another thing you can do is fire your motor in the dark. If there is any spark going to ground it will be far more obvious. Rick.

 

[johnsland8]

Re: 1993 15hp Johnson - removing plug wires while running question?

OK.. I got ya.

I will swap positions with them just to satisfy my curiosity but for the price of a couple of spark plugs I will replace them both anyway just to eliminate that as a possibility.

I will do it tomorrow and let you know what I find...

Thanks for the replies.

 

[R.Johnson]

Re: 1993 15hp Johnson - removing plug wires while running question?

I was joking of course, but feeling a shock does not take much voltage. Spark that won't fire an engine is still going to feel like one heck of a jolt.

 

[jonesg]

Re: 1993 15hp Johnson - removing plug wires while running question?

A sparkplug will not give you the required 7/16th inch test gap.
7/16th inch is almost 1/2 inch.

Get a proper gap tester from the automotive store, its a neat little (cheap) gadget that can pinpoint dying coils.

 

[johnsland8]

Re: 1993 15hp Johnson - removing plug wires while running question?

OK.. got back to it this afternoon finally.

I am happy to say that I swapped the plugs around and the problem followed the plug. So, two new plugs and she purrs like a kitten again.

I did have a question about the proper plugs though... I looked in the NGK and the Champion books and neither listed a 1993 15hp motor except for the commercial version. I'm pretty sure, based on the description in the manual and the model number (J15RLETB), that mine is not a commercial motor. They listed thru '92 and then from '94 on but no '93.. what gives? Which plugs should I use? I looked them up on the Evinrude parts look up and it gave 4 optional plug choices. It ran so well before the plug issue that I just replaced it with the plugs that were in there, but they were not listed anywhere in the books for any years of my motor. I used a BR9HS-10 NGK. Does anyone know what the proper plugs are?

Thanks again!

 

[Rick.]

Re: 1993 15hp Johnson - removing plug wires while running question?

Thanks for letting us know about your success. I'm not sure other than to say they should be champion. If no one responds you could try a new post with a topic line "proper plugs for 93- 15hp" and I'm sure someone will have a number for you. Have fun with your kitten. Rick.