1973 25 Hp. Johnson Running Rough

[7325johnsonhelp[]

It's definitely running rough. At last check I had spark to both cylinders. She cranks up fine and idols adequately but when its throttled up it sputters. it speeds up some but the rpms never get nearly as high as they should be. No power, tank run, in neutral, and circulating fresh water. I left it running long enough to get warm and held full throttle for a while. Seemed like she needed to cough one good time and it would catch and take off. Never did. Plugs have always been wet and oily but I haven't pulled them this last time. I'll go back through troubleshooting in the service manual. Suggestions are welcome. This thing is not that complicated and its getting on my nerves. Fuel system next?

 

[7325johnsonhelp[]

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.

I did try turning the high speed mix to lean till she coughed and back to normal. No help. Is that what you meant?

 

[7325johnsonhelp[]

Oh yeah, I disconnected the coils from the kill switch to make sure I wasn't dealing with similar symptoms from different sources but no change.

 

[7325johnsonhelp[]

It was running fine. It started sputtering at full throttle after running for about an hour. I ran it in that condition for about an hour getting back to the dock. The condenser for the top cylinder was found to be arcing. The condensers checked out okay on the multimeter and the arcing stopped after I rerouted the wire. Spark was restored to the plug. Is it possible the condenser is damaged, possibly from the arcing, and it is failing at full throttle, high demand? I'm going to change out the condensers with new ones. Cheap shot, fingers crossed.

 

[racerone]

I do not believe there is a high speed mixture needle on a 1973 model carburetor!

 

[7325johnsonhelp[]

I do not believe there is a high speed mixture needle on a 1973 model carburetor!

My bad, "low speed."

 

[7325johnsonhelp[]

lately, I've noticed what looks like fuel leaking out around the carburetor. Considering the motor seemed to be running fine and then suddenly began missing, at full throttle, could this be a carburation issue, possibly separate from the condenser/spark issue? I rebuilt the carb using a kit and its possible I screwed something up. I have another carb rebuild kit so I think I'll give it another shot paying very close attention to detail. This was a motor that I replaced or rebuilt most of the easy things before putting back into service after many years of sitting outside so there are many possible culprits. It has to be a spark or fuel issue, right? Unless it's a bad condenser or a wire arcing in the circuit I think the spark is good.

 

[oldboat1]

Go to an auto parts store and buy an adjustable spark tester (open air inline style). Try both leads at about 3/8" with both plugs out. Make sure you have a good ground for the tester. While at the store, see if you can borrow or rent a compression tester and see what you have.

 

[racerone]

Checked for blockage in the exhaust ?----Perhaps check lower crankshaft carbon seal.----Check fuel pump diaphragm.

 

[oldboat1]

Outside chance you might need a replacement flywheel, as you may have overtorqued using an impact wrench -- got an old time marina or shop in the area. I bought one last year for $10 (diff. motor). Impact wrench is fine for removing the nut, but risky for tightening back on. Need to clean the tapers and torque to specs.