Will a can of decarb help my idle?

Fish929

Seaman
Joined
Mar 29, 2009
Messages
50
Hey guys. I posted yesterday about my 1970 20HP Johnson not idling. If you give her some gas she's fine but if you don't she cuts off. The answer I got was to clean the carb. I went to the boat shop and they said to use this can of Motor Marine De-Carb. Think this will help?

Stupid question but where do I spray it? If I push the choke in the flap opens. Do I spray it in there?

Thanks for your help. I'm taking this "new" engine to the lake for the first time tomorrow.
 

Rick.

Captain
Joined
Jul 30, 2006
Messages
3,740
Re: Will a can of decarb help my idle?

I'm not sure if they were telling you to decarb. your engine or to use the Decarb. spray to clean your carb. with. If your using it as a carb. cleaner you need to pull the carb. apart and spray every orifice from both holes. The passages are the most important areas to clean. The throat and stuff will be cleaned well enough just by their proximity to the holes. Follow the spray cleaning with an abundance of compressed air, again, from each direction. Good luck. Rick.
 

Fish929

Seaman
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Mar 29, 2009
Messages
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Re: Will a can of decarb help my idle?

I'm not too sure I can tale the carb apart and put it back together properly. Would it hurt anything to decarb? AKA, warm up the engine, spray it in, wait fifteen minutes and then run it again per the directions on the can?
 

Rick.

Captain
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Jul 30, 2006
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Re: Will a can of decarb help my idle?

No it wouldn't hurt a thing. I'm just really surprised you have an idle problem and they told you to decarb. your cylinders and pistons. It won't hurt a bit and could improve your compression but it won't do much for your idle problem. Rick.
 

Mark_VTfisherman

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Nov 29, 2008
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1,489
Re: Will a can of decarb help my idle?

Probably won't hurt anything but I amnot sure you will be helping- the idle "circuit" or jet is probably plugged, which is why it will not idle, if the carb is the problem.

But, no, it won't hurt anything.
 

jbjennings

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Jul 18, 2007
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Re: Will a can of decarb help my idle?

Don't be scared of that carb, fish. You can handle it. Just use the little straw thing that comes with a can of carb cleaner and spray out all the little passages and such, and put a carb. kit in it which will have a needle and seat, several gaskets (including some that go with other motors since they use the same carb kit for several models) and packing washers for your slow speed adjustment screw/needle. Spraying that decarb stuff through the carb throat is a complete waste of time as far as getting it to idle better. A good decarb may be helpful, but as said already-----clean that carb!:)
Be especially sure you spray some cleaner through that low speed passage after you take out the screw that adjusts the low speed mixture and look in the carb throat while you're spraying so you can see if cleaner is coming out the 3 or 4 TINY holes in the top of the carb throat. In not, it still won't idle right and you'll have to soak it and spray carb cleaner or compressed air through there again. You can take out the little welch plug in the top of the carb and get to it that way, but most of the time I can get it clean without taking out the plug. If you don't know what a welch plug is, it's a little concave aluminum disk that fits in the hole in the top of the carb, and when you ping down on it the disk flattens and gets tight, sealing the plug.
BTW, the hard part on that carb is the high speed jet in the bottom of the bowl, but if your motor runs good wide open then it's already clean. An outboard carb. is not even in the same ballpark as the complexity of an automobile carb. You're going to laugh when you see how simple it is on the inside!
Good luck,
JBJ
 
Last edited:

jbjennings

Captain
Joined
Jul 18, 2007
Messages
3,903
Re: Will a can of decarb help my idle?

Oh, and don't forget to use eye protection when spraying that carb.
You DON'T want that stuff in your eye!!!!!!!!!!!!!!!
JBJ
 

EARLS BOAT

Petty Officer 2nd Class
Joined
Aug 2, 2008
Messages
143
Re: Will a can of decarb help my idle?

Those Carbs Are Easy To Take Apart And Clean. A Manual Is A Good Tool For Mantinece. The Timing And Carb Need To Be Syncernized For Best Performace, A Manual Will Tell You How To Do This As Well. If You Dont Have A Manual Use A Digital Camera To Take Pics As You Take It A Part So You Can See How It All Goes Back Together.
 

EARLS BOAT

Petty Officer 2nd Class
Joined
Aug 2, 2008
Messages
143
Re: Will a can of decarb help my idle?

Add Seafoam To Your Gas. It Is A Good Product For Cleaning The Fuel System.
 

Fish929

Seaman
Joined
Mar 29, 2009
Messages
50
Re: Will a can of decarb help my idle?

Thanks guys. I really appreciate it. That's a great idea about taking pics as you go along.

Thanks again!
 
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