Top Cylinder Not Firing

[Harry B.]

My 1977 Johnson 25 hp was running great WOT and then shut down to idle with the throttle wide open. It wouldn't start after that.
Upon closer inspection and trouble shooting, I've got no spark on the upper cylinder.

Is it the coil or could it be something else?

 

[jakedaawg]

try swapping coils top to bottom and see if problem moves

 

[kbait]

Check for worn/chafed wires coming from under the armature plate. If they're good, and coil swap still leaves the top cylinder w/o spark, you likely have a bad CD ignition box.

Good luck, and Merry Christmas!

 

[Harry B.]

Thanks much and Merry Christmas to you guys!!!!!

 

[Harry B.]

It's finally warmed up enough to play with the ol' outboard here in Utah.
I checked the wiring and it looks OK as far as I can tell. I changed out the coil and ignition from a donor motor that ran fine. I get some spark out of the different ignition, and none out of it with a swapped coil (before I changed the ignition), but for some reason, even with the different ignition, the motor doesn't advance to higher rpm despite opening the throttle all the way up.

Any suggestions on diagnosing the problem? Maybe I shouldn't be screwing around with used parts, but I'd likely replace them with used parts off the internet anyway on the donor motor and/or the broken one as I can't see putting hundreds of dollars in a outboard that's only worth a couple hundred in the first place being it's so old. .
Do I need a meter/testers to determine if the parts are faulty? The donor motor ran fine about a month ago.

 

[Fed]

Start again Harry.
All you've done so far is muddy the water by introducing unknown parts.
Put it all back the way it was.
Get a proper spark tester & test.
You will need to find out what the spark should jump in free air, 7/16" is advised for later motors but I don't know for sure about a '77 model.
If no spark on top cylinder then follow Jakedaawg's advice in post #2.

 

[oldboat1]

Agree on the testing, but add that it's an advantage to have the ignition parts from a runner to swap out for testing purposes (and poss. use). Successfully did something similar last summer. By the way, check the magnets in your flywheel.

 

[Harry B.]

I changed out the top coil for a new one and it now has weak spark compared to the bottom one. I changed out the ignition with similar/same results.
Any suggestions/recommendations?

 

[AlTn]

electric start or manual?...don't suppose it matters really since you do have a good spark to one cylinder the power pack is the likely culprit assuming the coil ground is good and the connections in the sockets are good

 

[Harry B.]

Manual start.

What's the chances of it being the stator? I've not pulled the flywheel, but I'd doubt I'd be able to diagnose it by just looking at it anyway. Is there a way to determine if the stator is bad?

I took the power pack off a running 1979 Evinrude and hooked it up and got the same results as with the original power pack.....good spark on the bottom cylinder and weak spark on the top.
It will finally fire and run, but It's still running on one cylinder.

To throw something else in the mix, when I was screwing around with the motor before I started checking for spark and it would start and run on both cylinders for a second or three, die and then wouldn't start again???????

I'll check the grounds and the wires again......just in case.

I surely appreciate you guys' time and help on this. This sucks hunting down electrical problems and I hate throwing parts at the problem.

 

[flyingscott]

Did you change the spark plugs at the very least swap those around. Do you have the coils with the plug wire attached or the newer style where it's separate. Check the pins in the connectors doesn't take much for those to break or the wires to come off of. And do you have electric start or manual they have 2 different stators

 

[AlTn]

nothing under the flywheel will provide spark to only 1 cylinder with the type of ignition you have < freakish exception I guess would be one of the flywheel magnets being inoperable >...the wires from the pp to the coils are orange with either a green or blue stripe....the blue stipe goes to the top plug...I'd check that wire from the pin in the socket to the coil...you can clean those socket connections with rubbing alcohol ...sand, file, whatever it takes to get to bare metal for the ground connections for the coils...if you have the newer coils they actually ground through the coil mounting points and are w/o a separate ground wire

 

[Harry B.]

Thanks for the recommendations.
It's a manual start.
I got a brand new coil with the spark plug wire attached and the ground wire is grounded good to the mounting coil mounting point. I cleaned and scraped that mounting point with a knife to bare metal..
I'll retrace my steps again and see if I can get better spark going. Thanks for shortening the hunt down on the top coil wire!!

 

[oldboat1]

It's usually a good idea to disconnect the kill switch when trying to troubleshoot -- unlikely to affect only one, but possible.

 

[Harry B.]

Wiring is fine as far as I can see.
How would I get more fire to that top cylinder? Its there, but it's weak. The bottom is a nice blue spark, the top a week thin silver spark.

 

[oldboat1]

Test with an open air spark tester, same setting and same ground for top and bottom. That the way you are testing?

 

[flyingscott]

What have you done with the spark plugs.

 

[Harry B.]

Yes, open air tester.

I changed out the spark plugs.

 

[AlTn]

if you have an inductive timing light....clip it to the bottom cylinder first and start the engine...observe the flash...does it ever not flash and goes dark for a few revolutions?..if so...you may have a failing charge coil under your f/w < looks like a coil > the only other component under there is the trigger sensor and you won't confuse the two

 

[oldboat1]

Went through a similar process with an '80s 9.9. Went from no spark on one of the cylinders (turned out to be a dead magnet), to weak spark on that cylinder. Replaced the sensor and the drive coil, and spark was restored.

That's the short story. Either through some testing or switching out parts, I ruled out the coils, power pack and stator (and discovered the magnet issue, which I hadn't run into before). My symptoms sound similar to yours on the problem cylinder. When I had spark, it bridged the 7/16 gap, but weak -- single spark, pale color. The other cylinder output was clearly sharper and brighter.

So based on that experience, I'll suggest it could be either the charge coil or sensor (or both, as I just replaced both out of frustration). If you have replacements in hand, you might try switching one or both.