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2000 Johnson 25hp 3cylinder

R

Ronniewhite

Regular Contributor
Motor runs fine until it gets hot. When I'm trolling it makes a poof noise every couple minutes and a puff of smoke. Is this a coil? It was running even worse. Once it got hot it did all the above put would quit completely. I found a little fuel line that was off and I put it back on. I think it was for the middle cylinder. I ran it for a hour today with muffs and after a half hour it started doing the poof thing but it didn't quit. I'm new on here . I hope I did this right and much thanks in advance 🙏.
 
It s a --- "much mis understood ''' ----thing on 2 strokes.----Caused by too little fuel in the low speed running.-----Or throttle plates opening to early.----Are the low speed mixtures set ?-----Where they set to a distance ?----Number of turns out ?------Is the oil injection still hooked up on this motor ?----Has the water pump impeller been replaced ?
 
Ok that's the little screw on the side? I pulled each plug wire of one at a time. The middle one didn't really seem to do anything when I did it. My neighbor said maybe a coil? I ordered one off ebay for 25dlrs. I might try this first. It should be here by Friday. If that doesn't work I will try the screw. I will let you know what happens. I appreciate the help
 
Ronniewhite said:
Ok that's the little screw on the side? I pulled each plug wire of one at a time. The middle one didn't really seem to do anything when I did it. My neighbor said maybe a coil? I ordered one off ebay for 25dlrs. I might try this first. It should be here by Friday. If that doesn't work I will try the screw. I will let you know what happens. I appreciate the help
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You started down the diagnostic trail but stopped short. Personally, I would have used an inline spark tester to confirm if the spark was present, absent, or weak. You can use an adjustable spark gap tester and these coils should create enough juice for the arc to jump a 7/16" gap when cranking with all spark plugs out. If it passes, the issue is not the the coil. If it fails, replace and retest. While you're waiting for your coil, head to a nearby autoparts store and pick up an adjustable inline tester like the one linked below. It only takes 15 minutes to do the test and it will confirm if the coil is needed.

It's possible you have an ignition component failing once it's heat soaked, but I'm thinking along with Racerone this sounds like a lean sneeze. When cold it's probably delivering just enough fuel but as the engine heats up you might be just under the needed fuel and that's your poof every now and then.

https://www.lislecorp.com/specialty-tools/ignition-spark-tester
 
So I got a adjustable ignition spark tester. The numbers on it are 10 20 30 40. We're should I ajust it to? And so I hook the plug wire on the end of it and clamp it to a bolt or something on the engine block and pull it over right?
 
Ronniewhite said:
So I got a adjustable ignition spark tester. The numbers on it are 10 20 30 40. We're should I ajust it to? And so I hook the plug wire on the end of it and clamp it to a bolt or something on the engine block and pull it over right?
Click to expand...
I believe Those are millimeter. 7/16” converts to about 11mm. Yes, put the plug wire in the end of the tester then clamp the other end to a clean ground.
 
I checked the coils with the spark tester. Coils are all good. It was jumping the gap at almost a inch so it's not a coil. I had it running today with the muffs and after about a half hour or so the poof of smoke started again. It only is doing it with the throttle down as low as it will go. If the throttle is turned up even the slightest it doesn't do it. Do you still think it's the slow speed needle? And we're is it? Sorry I don't know alot about motors. Just don't want to take it to a marina.
 
Also I think the top plug looked blacker then the other two. I'm going to take it out on the river tomorrow. Atleast on the river if it takes a dump the current will help me get back to the launch. Lol
 
Ya he did but he doesn't think that now after me showing him the spark. I changed the coil anyway that he thought didn't make a difference when unplugged but with it reved up a bit and unplugging the plug boot you can tell the difference on each one.
 
I was just reading through this again. Kevinj said when doing the coil test to have all the plugs out. I just had all the boots of the plugs and tested one at a time. Is that OK or should I have had the plugs out?
 
Had motor out on river Today for 4 hours. Put it thru all its paces. It worked great only poofed twice. Never quit lots of power. Maybe the coil was weak ��. Anyway it's good to go. Thx for the help everyone. ����
 
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