Carb, timing, or both?

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Wrboz
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Joined: 13 Oct 2020, 20:35
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Location: Wales,Ma

Carb, timing, or both?

Post by Wrboz »

I have a ‘86 Johnson 20 on a 14 foot boat. It starts hard. I can chug around all day at idle speed when I’m trolling. Basically idling in gear gives me 2.5-3.0gps speed. Pop it out of gear to land fish, back into gear to troll again. No problems. Runs for hours.
Trouble is, if I run it down the lake at speed, it will not start again. It stalls as soon as I throttle back. It will go 26.0gps opened up, with 2 adults onboard. It runs smoothly at WOT. But no way, no how will it start again, like until tomorrow. Anybody ever experience this? I thinking a carb rebuild is in order, but wondering if there’s something else I should be looking at also. Thanks, Bill

samuelh1987
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Location: Somerset, KY

Carb, timing, or both?

Post by samuelh1987 »

had a 25 do this exact thing. Ended up being a sheared flywheel key.

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DaleH
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Carb, timing, or both?

Post by DaleH »

Pappy, who posts on here is THE GURU, but it could be the idle adjustment. Usually if an OB stalls when backing off from crusing speed it is sign of improper idle speed adjustment, typically too lean. See photo, steps 6 and 7, but follow all.

BTW, you can buy these online for $20 or less in PDF form. Plus there is a post somewhere for access to free OB manuals already posted on this site, like a library.

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20Carb.jpg
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poorthang
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Carb, timing, or both?

Post by poorthang »

next time you go out, loosen the gas cap on the tank. not talking about the vent, but the cap itself. worked on a neighbors yamaha 25 last year. he had same problem. the chinese vent (rubber duckbill) in tank would not vent the pressure OUT! only in.

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Pappy
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Carb, timing, or both?

Post by Pappy »

First off.
Will not be a flywheel key so do not look for it.
Second, Tanks today are SUPPOSED to only vent in, not out. However saying that you are welcome to try the cap loosening to insure the tank is working properly. Usually the engine will start surging if it is starving for fuel and you did not mention this.

Now....Lets see if it is spark or fuel. We pretty much know it is not compression by the way you describe the running quality.
I think, on the 1986 that you have no air box on the front of the carb. Also you should have either an electric primer system or manual.
You are going to have to run the engine and duplicate the problem, hopefully ending up at the dock when it shuts down or you shut it down.
Once shut down and no longer starting I want you to pump the bulb in the fuel line and activate either the manual or electric primer and see if it starts immediately or at least tries to.
For spark, the easiest method for you is to carry a spare spark plug with you and disconnect both of the spark plug leads on the engine. Leave your other spark plugs in the engine. We do not want a fire.
Again, when the engine is not starting place the spare plug in one of the plug boots and lay the metal case against the powerhead or hold with a pair of insulated pliers. Observe a spark jumping the gap when you crank it.
Let us know the results of these checks and we will go from there.

Wrboz
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Joined: 13 Oct 2020, 20:35
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Location: Wales,Ma

Carb, timing, or both?

Post by Wrboz »

Thanks for the suggestions.Pappy you are correct, no air box on this model. I did as you said and duplicated the problem. 1: I am getting a spark. 2: I pumped the bulb and activated the electric primer; it doesn’t make any difference. Also, the slow speed-knob on the carb is adjusted correctly per the literature. So what’s the next step?

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Pappy
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Carb, timing, or both?

Post by Pappy »

Wow.....forgot about this thread. Sorry.
Okay we know that spark is not the issue.
Now we go for a "is it rich or is it lean" issue and we check the primer nipple to see if it is clear as well.
When it does not start pull the plugs and look at them. Dry? Wet?
Take off the hose at the primer solenoid that leads to the primer nipple. Can you blow through it while connected to the primer nipple? If not take a piece of wire leader or a piano wire or a piece of tag wire and pass it through. I think the hole is only around .014" or so.

Wrboz
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Joined: 13 Oct 2020, 20:35
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Location: Wales,Ma

Carb, timing, or both?

Post by Wrboz »

Thanks Pappy. It’s gonna take a week or two before I can get the boat back in the water. My tow vehicle has electrical problems that need to be straightened out first. I will do as you suggest and post the results in a couple of weeks. Thanks again! - Bill