1973 25 Hp. Johnson Running Rough

[7325johnsonhelp[]

Me again. Same motor, new issue. After the water circulation issue was solved, I took the motor to the lake. It ran fine for approximately an hour, mostly full throttle, sat off for a couple of hours, and then started fine for the return trip. About 10 minutes in, full throttle, it started "missing". Within a few minutes it was "missing" so bad the boat came off plane. The motor would continue to run until I got back, about 20 minutes, but it was very weak, regardless of throttle position. Lots of smoke, I believe oil. It would occasionally seem to catch" but never for long enough to get back on plane before returning to "missing". It continued to idle rough at the landing and even restarted easily when loading on the trailer, but still running rough.
When I got home, I noticed lots of gray sludge around the prop and general foot area. The motor is up using a transom saver for transport. I first suspected some foot issue as well but now believe that was just unburnt oil/water drainage from the vent holes and exhaust. The foot lube is still fine and water free and no leaks detected after several days.
I removed the plugs. new Champion UJ4J gapped at .030. They were both wet and black. Compression is good and unchanged at 138/140 psi both cylinders. I turned the motor over with the plugs out to see if they were sparking. They sparked only very intermittently, not on every rotation, not even close.
Now when I serviced this motor, I replaced both ignition coils, points, plugs, and condensers among many other things. I did not replace the driver coil. Points were gapped @ .022 as instructed by the service manual, since they were new. Gas is Ethanol free mixed 50/1 with OMC oil.
Seems to me that since both plugs are not firing as I think they should my next stop is the driver coil. I need to recheck the point gap anyway. Suggestions?
Any help is appreciated. Racerone your experience with these motors is invaluable and your thoughts would be greatly appreciated. Just let me know if you want me to check something or post images.

 

[saltchuckmatt]

Me again. Same motor, new issue. After the water circulation issue was solved, I took the motor to the lake. It ran fine for approximately an hour, mostly full throttle, sat off for a couple of hours, and then started fine for the return trip. About 10 minutes in, full throttle, it started "missing". Within a few minutes it was "missing" so bad the boat came off plane. The motor would continue to run until I got back, about 20 minutes, but it was very weak, regardless of throttle position. Lots of smoke, I believe oil. It would occasionally seem to catch" but never for long enough to get back on plane before returning to "missing". It continued to idle rough at the landing and even restarted easily when loading on the trailer, but still running rough.
When I got home, I noticed lots of gray sludge around the prop and general foot area. The motor is up using a transom saver for transport. I first suspected some foot issue as well but now believe that was just unburnt oil/water drainage from the vent holes and exhaust. The foot lube is still fine and water free and no leaks detected after several days.
I removed the plugs. new Champion UJ4J gapped at .030. They were both wet and black. Compression is good and unchanged at 138/140 psi both cylinders. I turned the motor over with the plugs out to see if they were sparking. They sparked only very intermittently, not on every rotation, not even close.
Now when I serviced this motor, I replaced both ignition coils, points, plugs, and condensers among many other things. I did not replace the driver coil. Points were gapped @ .022 as instructed by the service manual, since they were new. Gas is Ethanol free mixed 50/1 with OMC oil.
Seems to me that since both plugs are not firing as I think they should my next stop is the driver coil. I need to recheck the point gap anyway. Suggestions?
Any help is appreciated. Racerone your experience with these motors is invaluable and your thoughts would be greatly appreciated. Just let me know if you want me to check something or post images.

Sure seems like it has to be.

 

[tphoyt]

Could be the flywheel key. Did you torque the flywheel last time or lap the taper’s?

 

[7325johnsonhelp[]

Could be the flywheel key. Did you torque the flywheel last time or lap the taper’s?

"Lap the tapers"? I used an impact wrench. I'll check the key when I pull the flywheel to replace the driver coil.

 

[tphoyt]

Lapping the flywheel along with proper toque ie not an impact gun ensures a locking tapper. The key is only there to locate the timing. The tappers drive the flywheel.
Lapping compound commonly known as valve grinding compound is used to lap the flywheel to the crank so they mate and lock properly. If you sheared the key it would cause the problem you are having in my eyes.
I’m sure other will chime in and it may not be the problem but worth checking out.

 

[7325johnsonhelp[]

Update; No spark top cylinder. I just replaced the driver coil and no change. Pulled both plugs, left one in the boot and turned over the motor. Took turns with each plug. No spark top cylinder. Swapped out top ignition coil with one from a similar motor, no spark. Swapped out the two new ignition coils, top to bottom, still no spark on top. Bottom sparked fine. Took wire Brush to all grounding surfaces, no change. Followed all wires and connections back to flywheel. They look fine, no apparent damage.
Points, condensers, plugs all new, before this incident. Readjusted gap on points to .020 when I replaced the driver coil and inspected all connections. Everything looked fine. Is it possible a new condenser failed? Is it time to break out the VOM? Help?

 

[kbait]

Perhaps the kill wire that connects to the top cylinders pointset is grounded? Pull kill wire off pointset and test for continuity to ground. If it’s grounded, trace the wire back.. probably chafed. If kill wire tests good, may as well swap condensers and re-test..

 

[7325johnsonhelp[]

Thanks. I'll do that. When I was running the wires from the ignition coils down I wondered about that as my kill switch is old and looks pretty worn.

 

[racerone]

Look for broken wire / bad connection somewhere.

 

[7325johnsonhelp[]

In turn, I disconnected each coil/points from the kill switch where the two wires connect to one and checked continuity from the connection /one wire through the kill switch to battery/frame ground, no continuity regardless of kill switch position for either connector. The only continuity reading I could obtain was between both connectors when the kill switch was pressed and it was jumping around, meter set at 20k.
Am I wrong in assuming the kill switch works by grounding each of the two ignition circuits? Shouldn't I get continuity from either connector to battery ground when the kill switch is pressed? If the top cylinder is not firing because the kill switch is grounding it why aren't I getting continuity from the top cylinder connection to ground?
Seems to me the kill switch is behaving badly. Maybe just badly grounded?

 

[7325johnsonhelp[]

Lastly, can't I confirm a problem with the kill circuit by just disconnecting the switch where in connects to each coil and running the motor?

 

[saltchuckmatt]

Lastly, can't I confirm a problem with the kill circuit by just disconnecting the switch where in connects to each coil and running the motor?

In turn, I disconnected each coil/points from the kill switch where the two wires connect to one and checked continuity from the connection /one wire through the kill switch to battery/frame ground, no continuity regardless of kill switch position for either connector. The only continuity reading I could obtain was between both connectors when the kill switch was pressed and it was jumping around, meter set at 20k.
Am I wrong in assuming the kill switch works by grounding each of the two ignition circuits? Shouldn't I get continuity from either connector to battery ground when the kill switch is pressed? If the top cylinder is not firing because the kill switch is grounding it why aren't I getting continuity from the top cylinder connection to ground?
Seems to me the kill switch is behaving badly. Maybe just badly grounded?

Sometimes kill switches will test correctly with continuity but not work right. Many more volts going through them.

I would unhook them and see if the top cylinder fires.

 

[7325johnsonhelp[]

Disconnected coils from kill switch, pulled plugs, turn over motor... no spark top, bottom spark fine. I've inspected all the wires and connections involved and they all look good to me. Next stop, multimeter on the condensers I suppose.
I tuned my first car, a 68 Camaro, "under the shade tree". I remember after one tuning she ran very rough. Drove me nuts for hours. An older shade tree told me to put the old condenser back. She ran fine. What are the odds?
You know you're old when you can remember gapping points with a "pop-top".

 

[saltchuckmatt]

Disconnected coils from kill switch, pulled plugs, turn over motor... no spark top, bottom spark fine. I've inspected all the wires and connections involved and they all look good to me. Next stop, multimeter on the condensers I suppose.
I tuned my first car, a 68 Camaro, "under the shade tree". I remember after one tuning she ran very rough. Drove me nuts for hours. An older shade tree told me to put the old condenser back. She ran fine. What are the odds?
You know you're old when you can remember gapping points with a "pop-top".

That's really the only thing left that it can be, right?

 

[7325johnsonhelp[]

I checked both condensers and they're good. However,

Look like an issue to anyone?

 

[7325johnsonhelp[]

 

[7325johnsonhelp[]

I redirected the wires, buttoned it up, pulled the plugs, and she sparked fine! Duh!

 

[saltchuckmatt]

View attachment 371714

A little grounding corrosion?

 

[7325johnsonhelp[]

I've been "probably" over thinking this. The motor ran fine after the tune up for about an hour, various throttle positions, before it started missing.
I'm thinking a combination of distance, time, and insulation. I think it was insulated and far enough away, barely, from the condenser case that everything went fine for little while. I think the first jump probably set the path and it cascaded from there.
I definitely have spark again. I cleaned, wire brush, and re-gaped the plugs. She still runs rough and smokes a lot at high throttle in the tank. Should I just replace the plugs and expect it to take a few minutes to "clean-up" at full throttle after running so long on one cylinder?

 

[saltchuckmatt]

I've been "probably" over thinking this. The motor ran fine after the tune up for about an hour, various throttle positions, before it started missing.
I'm thinking a combination of distance, time, and insulation. I think it was insulated and far enough away, barely, from the condenser case that everything went fine for little while. I think the first jump probably set the path and it cascaded from there.
I definitely have spark again. I cleaned, wire brush, and re-gaped the plugs. She still runs rough and smokes a lot at high throttle in the tank. Should I just replace the plugs and expect it to take a few minutes to "clean-up" at full throttle after running so long on one cylinder?

Did you re-dial in the carb....lean it out until it sneezes and then open it a 1/4?

Might just need a good run in the lake.