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1972 Johnson 25 hp, elec start... back from the dead!

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randyj

Regular Contributor
I acquired this motor a couple of months ago, no fire, sat up a few years. To get it firing I replaced one coil and both condensers, cleaned and set the points.020. Without touching the carburetor it cranked and ran good out of the water. I put it on a small boat today and it did kind of okay when I idled out. Once I got in the open I throttled up. It slowly increased rpm but tended to sputter. The more I ran it the better it got up to a point. Then like magic it would sputter some then take off and ran fantastic for maybe 100 yards to 1/4 mile..then act like it was only hitting on one cylinder. I tore it back down to find a plug wire loosely fitting in one coil. While I had it down I went through the carburetor...spotless! The guy I got it from had the carb cleaned before putting in storage years ago. I did the ritual cleaning of everything in the carb and reassembled. Now it's a little hard to crank, still sputters and from the looks of the exhaust is running extremely rich with black oily gas/carbon coming out the exhaust. I can't tell if it's just not always firing or if it is flooding causing it not to fire. Just need a little help thinking on this ....
 
Have you inspected the pistons for carbon build up? Even though a carb looks clean it may not.
Have you checked compression? hows that spark does it jump 1/4 inch with a blue spark? Are the fuel lines old cracked and sucking air.
 
when you cleaned the carb did you replace the (RED) adjustment needle Retainer? if not you will need to do this, did you adjust the carb?, warm the motor if the motor is running rich you need to turn the adj needle to the right 1/8 turn at a time until the motor sputters, then back it off 1/8 turn.
 
Get a pair of plastic pliers from any auto parts store and remove one plug wire at a time to see if it operating on 2 cylinders....you can also use your hand to compare cylinder head temperature to see if both cylinders are firing...Not sure why you didn't replace both coils while you had it apart...If it is running on one cylinder it is spewing out 1/2 of the raw fuel it is using...one way to confirm a weak spark is to temporarily adjust the plug gap to .010....sometimes even a weak coil can jump that gap...this is sometimes a good trick to return to the dock in an emergency. A compression test would also help prevent going off in the wrong direction and replacing parts that may not need replacing.
 
Not sure why I never got back to this thread, but to follow up I did get the motor running smoothly and for a 30 year old motor from the bone yard it is quite dependable. All the major running issues were in the ignition system, pretty much one coil and the condensers. Cleaning up and/or replacing the points helped and for the most part this engine has run almost flawlessly for almost 2 years with only one carburetor cleaning this spring. The biggest culprit was actually one condenser intermittently firing.
 
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