84 140hp johnson questions

R

rascle4

Recruit
Joined
Jun 28, 2009
Messages
1
Hi every one.This is my first post.My engine i bought from a guy recomended by a friend .He has a shop in baltimore.he sold me the motor and rebuilt it and installed about 7 years ago.It runs real good still but it never idled good sneezes and stall while trolling.and always felt like vibrates at idle . never ever had any problem.so ive bin looking into trying to make smoother idle and i did compresion test it shows around 65 lbs in all the cylinders.it still runs as good as it did after rebuild.could of this guy used differnt heads or something that has compresion this low and still run well?
 
tashasdaddy

tashasdaddy

Honorary Moderator Emeritus
Joined
Nov 11, 2005
Messages
51,019
Re: 84 140hp johnson questions

i would recheck compression, with a different guage. guages are different. directions. http://forums.iboats.com/showthread.php?t=313884

you present reading are low, and would cause a poor idle. i would try to decarb the motor.


Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck
 
E

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: 84 140hp johnson questions

Your compression is really low for a 140- about half what it should be. You need to sort out this compression issue first-you are about half what it should be. Follow Tas' comments. Further, lean sneezing at idle can occur if at least one of the idle circuits/passages is not working properly. I'd pull the carbs and use an aerosol can of carb cleaner to check the flow on all 4 idle circuits. Pull the idle jets first. Check all 4 and compare them, they all should flow the carb cleaner spray at the same rate. Possible one of them has some dried fuel in it, limiting fuel flow.. It will also cause the symptoms you describe.
 
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