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scotty B

18 horse johnson

10 posts in this topic

Hello all

I have a 18 horse jonson and when i try to troll with it or go to slow it boggs down and quits on me. Any suggestions on what this could be or what i could do to prevent this from happening besides using a different motor? I would appreciate any help i could get.

Regards: Scotty B

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Weird, when I give mine gas it kills. Just opposite of yours. I changed out the plugs, which was a good thing cause mine were shot. So check that.

Next is to get some carb cleaning fluid and look in the carb and see if gunk is clinging. Clean that off with paper towel or something, then spray it down with the cleaner.

If you can adjust the carb while the motor is running (garbage can full of water or that suction cup thing) that might help to. Very little adjustment, tap tap tappy! (Happy Gilmore)

But for all it's worth I did all of this except adjut the carb while it ran and mine still kills sometimes when I give it the gas.

It's places to start though. I'm sure other people will post here soon enough.

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Hey EBass thanks for the advise i will give those things a try and hopefully it works. It seems like most of the time it boggs and kills is when i'm getting a hit. Thank you scotty B

[This message has been edited by scotty B (edited 08-12-2003).]

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Yup actually it was replaced five years ago or so. That was pretty tuff trying to find pieces for an old motor around pelican rapids.


Scotty B

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I have the same exact motor that is doing the same thing as yours Scotty. Wide open, runs great, can't troll without it killing. I've changed the plugs, run Sea Foam through a tank of gas, and sprayed close to a can of carb cleaner through her. Still won't idle down. I would be interested to hear what the outcome is...

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If you cant get it to idle with the low speed adjustment then its most likely plugged with gum, dirt or corrosion. Sea Foam is a great product but it's not for cleaning carbs. Only one thing will and thats carb cleaner like Gumout. Running carb cleaner in the gas is a crap shoot. Your lucky if it works.

Its possible that your engine runs great at high speeds but not so good at low speed. It does rule out a bad fuel pump, lines and bulb. Only one remedy and thats clean the carb. Turn the high and low speed adjustment all the way and count the turns till it stops, don't tighten them. Counting the turns gives you a reference on where to start your tuning. Now back them all the way out. Don't lose any parts, spring, steel washer, rubber washer and needle. Next steps are dependant on your carbs make. I know you 2 are going to have a bowl, take it off. Carefull not to lose anything. When the bowl drops you'll see a little rocket ship, that stops the fuel when the bowl fills with gas via the float rising. Now soak everything over night in Carb Cleaner. Blow it out with compressed air while the carb is still wet with cleaner. You'll see little holes, gas has to go threw them. Use a bread twister wire to make sure their not plugged. Use carb cleaner in a spray can to blow through them. In other words if theres a hole clean it!

Put your little rocket back in it's hole. replace the float(hope you didn't bend the tang the rocket sits on). Now hold the carb upright and lift the bowl up and down. The rocket should go up and down to and not stick. Replace the bowl. Replace the needles, you counted your turns. This will get you close when its time to adjust the carb.
Even if you know what your doing a manual is a small investment. I have one for most my stuff. Get one thats specific to your engine only. Applications you dont have will just confuse you, well me anyway smile.gif Lay down newspaper on a big table with good lighting and have at it.

[This message has been edited by Surface Tension (edited 08-12-2003).]

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Before you do the teardown, make sure your tank is maintaining pressure. I cleaned and painted a tank years ago and neglected the washers that sit under the screw heads. I wasn't getting a good seal and there wasn't enough pressure in the tank to feed fuel. After getting the new washers installed, motor was back to normal.

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Thank you everybody for all the advice. It is a pretty old motor but i dont want to buy a new one if i don't have to. I will check out everything and see if i can get it running right then i will post to let everyone know Thank You: scotty b

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