Johnson 25 missing

[Shooter Too]

I have a 1999 (date on engine is 12-08-98) Johnson J25REEN Serial number 04677730 2 cylinder 2 stroke outboard. I bought it used last February and have not had a problem until two weeks ago. It started missing at idle. The miss is not noticable at running speed. Sometimes the miss is accompanied by a backfire that shuts down the engine. The miss is worse at 1/4 throttle like when I am trying to pull away from the dock. That is usually when I get the backfire.<br /><br />While on the hose and idleing I can pull the lower plug wire off with no effect on the engine running. Putting the lower wire on and pulling the top wire shuts down the engine. I thought this indicated a bad coil so I replaced the bottom coil today with no effect. <br /><br />Where do I go from here?

 

[Waterbugtoo]

Re: Johnson 25 missing

Check fire and compression on both cylinders. Are they good? What do the plugs look like? Save some money, dont keep guessing the problem. Find it and fix it instead of trial and error. <br /><br />

 

[Bear]

Re: Johnson 25 missing

Hi!<br />Clean the bottom spark plug. Switch them two. Try again. If the problem moves you got it. Next thing is to switch the spark plug wires.

 

[Shooter Too]

Re: Johnson 25 missing

The first thing I did was put new plugs in. Then I switched them, neither had any effect on the problem. That is why I started trying other things like pulling the plug wires. <br /><br />The bottom plug is wet/oily after the engine has run for a little while, ten minutes or so. <br /><br />I will switch the wires and give that a try. What should the compression be?

 

[Bear]

Re: Johnson 25 missing

The wet and oily spark plug is normal as you don't have a spark all the time. <br />I don't know the numbers but the compression must be within 10 percent at least.<br /><br />Check the spark plug boot and the spark plug wire. If it is long enough you can cut it about half an inch. IF that was the problem.<br /><br />Also check all connections and ground.

 

[Walker]

Re: Johnson 25 missing

Give the carb a good cleaning. Sounds like your idle circuit is not flowing enough fuel. The backfire you are experiencing is normally caused by a lean condition.

 

[Shooter Too]

Re: Johnson 25 missing

OK, Here's where I am on this thing. Compression is between 105 and 110 psi on both cylinders. New plugs. Swapped plug wires, plugs and even coils without a change in symptoms. Rebuilt carb, checked filter screen on fuel pump, cleaned gas tank and refueled with new gas. <br /><br />Where do I look next?

 

[Bear]

Re: Johnson 25 missing

"without a change in symptoms" Did the problem move to the upper spark plug?

 

[Shooter Too]

Re: Johnson 25 missing

No, the problem has stayed with the bottom cylinder. That is why I was so sure it was the coil. I removed the bottom plugwire without change, but if I remove the top it won't start. I looked at the reed plate and cannot see anything that looks suspicous. I would take it to the shop except it would take away some Christmas money. I hate being shipwrecked like this. I usually do most of my hunting in areas that are only accessable by boat.

 

[fishinhole]

Re: Johnson 25 missing

shooter too if you have a voltage meter ck. to see how much voltage you have on the wire that goes to the coils, should be 100-300 volts. if the same, one coil is not firing. if not good power pack or stator is bad. next ck. wires going from to power pack to stator, should have 1 to 6 volts, if not stator is bad

 

[Shooter Too]

Re: Johnson 25 missing

Thanks Fishinhole, I do have a volt meter. How do I perform the checks you recomend?

 

[fishinhole]

Re: Johnson 25 missing

CONNECT BLACK WIRE ON VOLTAGE METER TO GOOD GROUND, IF RED WIRE LEAD IS POINTED, JUST POKE IT IN WIRES AND SEAL THE LITTLE HOLE WITH LIQUID TAPE