68 johnson 20hp idle kicks/bucks/shakes.

snake eater

Seaman Apprentice
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Oct 20, 2009
Messages
32
Hello, I recently bought a 1968 Johnson 20hp fd-22m, nice clean motor, I replaced the fuel pump/ all the electrical/ needle valve/ and water pump. When I start it up cold (with choke) it runs good, but as soon as I put it to half choke or no choke its starts to shake and kick bad, I have some experience with outboards, but I am not sure what to check next, any suggestions would be great, I would like to take it out before the winter sets in.
 

oldrudedude

Chief Petty Officer
Joined
Jul 3, 2008
Messages
480
Re: 68 johnson 20hp idle kicks/bucks/shakes.

Sounds like fuel starvation. Low speed jets/needles clogged or need adjusting? Carbs need cleaning? Start there.
 

bktheking

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Re: 68 johnson 20hp idle kicks/bucks/shakes.

It not getting enough gas at idle, have you played with the slow speed needle to allow more fuel at idle?
 

a70eliminator

Captain
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Sep 9, 2007
Messages
3,688
Re: 68 johnson 20hp idle kicks/bucks/shakes.

Carburetor air fuel mixture too lean, thats when you get that bucking spitting condition, turn the knob screw or whatever it is to rich direction, not familiar with your peticular carb.
 

snake eater

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Re: 68 johnson 20hp idle kicks/bucks/shakes.

I cleaned the carb passages today and just took out the slow speed needle. It has a groove in it and is slightly bent. I tested it and it shuts off the fuel supply but I'm guessing its blocking the fuel flow, wouldn't turning the needle out correct this problem? or does it block fuel flow even with a slight bent no matter how many turns out?
 

oldrudedude

Chief Petty Officer
Joined
Jul 3, 2008
Messages
480
Re: 68 johnson 20hp idle kicks/bucks/shakes.

I think you need a new needle, but if it was me I would try to staighten it, machine the groove out with some fine sandpaper, and turn it out a little more to get a richer mixture. It is going to be difficult to get it right without working the end of the needle because now the end of the needle that extends past the groove is acting as a plug.

Do you know what the default setting for that screw is?
 

bktheking

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Re: 68 johnson 20hp idle kicks/bucks/shakes.

It would but if it's bent that's a problem all in itself, the needle on the end has to be straight.
 

snake eater

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Oct 20, 2009
Messages
32
Re: 68 johnson 20hp idle kicks/bucks/shakes.

well in any case I will go to my marine store tomorrow and get one they have a bunch of parts laying around. I'm pretty sure the stock setting is 1-1/2 turns out, but usually I just turn it until it runs then fine tune it. I did try turning it out as much as possible when I had the motor running and it seemed to make no difference.
 

bktheking

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Joined
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Messages
5,057
Re: 68 johnson 20hp idle kicks/bucks/shakes.

They show as available, part # is 0308349.

Cheers
 

snake eater

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Joined
Oct 20, 2009
Messages
32
Re: 68 johnson 20hp idle kicks/bucks/shakes.

well I got the new needle today, the needle works alot better but didnt solve the problem, so i looked into the throttle linkage and sure enough somebody tried to repair the throttle cam arm (badly I might ad) long story short, when they welded the broken part on they screwed up the angle, so at no throttle the throttle plate was open by at least a quarter. I had a new arm laying around, put it on and WOW what a difference I took it out to the lake and it ran absolutely perfect, thanks guys for your help.
 
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