20 HP Johnson won't idle

alexd

Recruit
Joined
Jul 5, 2002
Messages
2
I have a 20 horsepower Johnson Seahorse (model# 20CR79R serial#C8054451). It is very hard to start and when it does it won't idle. It runs fine at full rpm although it does seem a bit sluggish. Also, what year would this motot be?<br />Thanks
 

fireman 757

Petty Officer 1st Class
Joined
May 18, 2002
Messages
276
Re: 20 HP Johnson won't idle

don't what year it is but you could have a couple of problems. When it is running does your primer bulb go soft? Have you cleaned/rebuilt your carb? Sounds like you have some gunk in your high speed jet or you have dropped a cylinder. Check for spark at idle. Pull a plug wire and see if it changes anything. Then replace and pull the other. What happens? If one does not change your running the ignition coil to that plug is probably bad.
 

Bear

Lieutenant Commander
Joined
Mar 1, 2001
Messages
1,627
Re: 20 HP Johnson won't idle

20CR79-20CRL79 20 HP: 1979 <br /><br />/Bear
 

jimraelee

Cadet
Joined
Jun 8, 2002
Messages
12
Re: 20 HP Johnson won't idle

alexd... sounds more like low speed mixture adj to me... just had my 18hp evinrude apart before the big weekend... and took some time to get the low speed mixutre screw tuned in. Until then it also was hard to start and keep running at low speed. Now starts on 2/3 pulls and idles ok.... jim
 

alexd

Recruit
Joined
Jul 5, 2002
Messages
2
Re: 20 HP Johnson won't idle

Spark is good to both cylinders and I had a mechanic clean the carb last week. After running for a couple of minutes you can give the primer bulb 1 or 2 squeezes. I'll try a compression test and see what it says.<br />Thanks!
 

ShafferNY

Petty Officer 1st Class
Joined
Jun 7, 2002
Messages
232
Re: 20 HP Johnson won't idle

I'm with jbutter on this one, sounds like your low speed circuit may be dirty still. Does you motor have an inline fuel filter? If not install one between the pump and the carb and clean the carb out again.
 
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