25 HP Johnson idling issue

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east514

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Jun 21, 2012
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I have a J25RESB (1990 25HP tiller steer) outboard that belonged to my father in law. He passed away 7 years ago and the boat has set up ever since. My mother in law told me the boat was mine to do what I pleased with it. I pulled the boat home, placed fresh gas in the tank and the thing started right up and ran like a top! I replaced the water pump, rebuilt the carb (although I was not pleased with the carb kit. It only contained a new float valve, float, and gaskets), replaced the starter pawls, new plugs, fuel line, and filled the tank with non ethanol fuel. Motor runs like a dream at full throttle but refuses to idle. My wife and I love catfishing (trot lines or jug) so idling is a near must. I'm at my ropes end on what to do and tired of nursing the blisters the pull rope has created. I just tried adjusting the needle valve (which I'm under the impression adjusts fuel mixture) and still no success. I've adjusted all the way to both ends of the spectrum and still no luck. Because of my male ego, I'm refusing to take the thing to a shop unless I have to, so I'm hoping someone here can help me out.
 

oldcatamount

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Apr 4, 2010
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1,740
Re: 25 HP Johnson idling issue

Do a compression test and a spark test first. A bad head gasket and/or a weak coil will cause it to not idle.
 

east514

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Jun 21, 2012
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Re: 25 HP Johnson idling issue

I think I'm pretty close now. I went back out and tinkered some more with the carburetor. It will idle now and run smooth but in order to keep it alive you have to give just a little throttle. I haven't done an actual compression test or spark test. But I have checked compression by placing my finger over the spark plug hole and it has enough compression to blow my finger off. And I tested spark by placing a screw driver in the plug wire and grounded it to the block while someone pulls the rope. I know these aren't true tests, but I did what I could with what I had. I appreciate the reply. I'm going to take the boat out tomorrow to see how it does on the water.
 

oldcatamount

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Re: 25 HP Johnson idling issue

Turn the low speed needle valve all the way in (clockwise) and seat it lightly, then back it out about 1 and 1/2 turns (clockwise). Should get you in the general vicinity of a good running motor. Play with it tomorrow while on the water to get it fine tuned.
 

Daboz

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Dec 30, 2015
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1
I have a 25 hp Johnson seahorse 1972 that runs good but when I have to idle my does the same thing. Hope I can find the fix
 

steelespike

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Apr 26, 2002
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19,069
Definitely do your own thread. There is a tab near the top of the E/J forum.(new topic)
Tell us what you have tried.
 
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