72 20hp johnson idle needle too rich?

[dkonrai]

i am going nuts on this motor. i picked up this pretty clean 72 johnson 20hp. po said it was his grandfathers and was in a shed for the past 30 years. seems like it was well cared for.
it starts, pretty easy actually. i have low idle issues, almost like a vacum leak? the idle screw is only out 1/2 turn. any more and it starts to run really rich/dies. i have not taken it out on the water yet, till she is bucket ready.
new fuel pump
rebuilt carb, blew out orifices, set float, pulled and replaced the pot plugs. (i think someone did try and work on the carb, all new floats/needle/etc. ) i replaced the needle/seat/set the float.
new hoses, even the small 1/8 inch lines to the crank case.
have i missed something?
oh and sanded the carb base to make sure it was flat.
dino

 

[F_R]

Re: 72 20hp johnson idle needle too rich?

Running too rich with the idle needle open 1/2 turns suggests a cople of possibilities:

1. How about the fuel pump diaphragm? If leaking through it, it will run rich.

2. You probably would have noticed, but how about a grooved taper on the idle needle?

3. Related, perhaps somebody has buggered up the seat for the idle needle?

4. Is the idle needle actually going all the way in to the seat? It may be stopping short and actually is more than 1/2 turn off the seat.

5. Lastly, I know I'll hear a bunch of protests about how well their motor idles, but the '72 was a lousy idleing motor. Most people wouldn't notice unless they know how well earlier models idled. The culprit is they cleaned it up in the interest of environmental pollution. They modified the crankcase drain system to where they ran lousy. Try pulling the hose off the upper bypass cover and let it squirt overboard (temporarilly), and plug the nipple in the bypass cover. Run better?

EDIT: I keep forgetting it is winter up north, and everybody is running motors in a tank or barrel. Is that what you are doing? And do you have the motor hood on while you are doing it? If so, there is your answer.

 

[dkonrai]

Re: 72 20hp johnson idle needle too rich?

fr,
wow that was a fast reply

i replaced the fuel pump, actually had some spare parts laying around. fp was pulled off a running motor (dont ask how many johnnyrudes are on the property..)

needle looks new, as if it was replaced? or it is really a low hour motor.

idle needle seat looks ok, i used a led flashlight and looked down the seat. i bought a needle bushing thinking that would be the problem, but i cant seem to figure out how the bushing fits in? bushing stops at the needle step, so i cant thread the needle in the threads, i.e. the bush pushes the needle out too far preventing the needle from threading in. the needle seal was absent when i took apart the carb.

i think the needle is seating. dont want to push too hard, judging by the threads sticking out of the base, i believe its lightly seated.

thanks for the tip on pulling the upper hose and plugging it. i used yellow hoses, from the lawn mower shop so i can see the crank case pulses of fuel. there is another hose that runs from the intake to the lower case as well. i bought this for my 14 foot tin. thought was that it would be about the same weight as a 15hp, but more cubes=more torque= more fun. i fish and troll so i had hoped she would idle down for a slow troll 1.3-1.6 mph is the goal. at wot i would be happy to see 20mph? i weigh 170, the boat is about 200.

i live in california, its not that cold. i wanted to barrel run it before i water test it. and i have the hood off, too lazy to pull it on and off when im test running the motor.

last note, it pees like a race horse! changed the impeller and i cant believe how robust the water coming out the exhaust. engine stays pretty cool

dino

 

[AlTn]

Re: 72 20hp johnson idle needle too rich?

marineengine.com..evinrude parts..your year and hp....carb...are parts #'s 35 and 41 what you're referring to?

 

[dkonrai]

Re: 72 20hp johnson idle needle too rich?

marineengine.com..evinrude parts..your year and hp....carb...are parts #'s 35 and 41 what you're referring to?

yes parts 35,41. part 41 was easy, part 35 doesnt fit in the carb. it fits, it just wont allow the needle to thread into the base. it seems the bushing is too large.
dino

 

[AlTn]

Re: 72 20hp johnson idle needle too rich?

k..experiencing same symptoms with a '72, 25 hp...terrible idle and having to reset the idle mixture each time the engine was started cold. I found a nos needle on ebay which is different from the one presently installed. I can see that if the portion of the needle between the threads and the beginning of the taper < the "barrel" of the needle?> was too thick then the needle valve bearing couldn't compress enough to allow it to fit into the seat. If that's what you're experiencing, maybe this isn't the correct needle ? Has the engine ever idled well? As the 25 hp. I have sits now, I doubt it'd ever be "good" as a trolling motor.

 

[jasper60103]

Re: 72 20hp johnson idle needle too rich?

yes parts 35,41. part 41 was easy, part 35 doesnt fit in the carb. it fits, it just wont allow the needle to thread into the base. it seems the bushing is too large.
dino

Just curious. I actually never changed 35. Was it difficult to remove?

jasper

 

[dkonrai]

Re: 72 20hp johnson idle needle too rich?

i used a probe to feel around and it is not in the carb base. used a bright 300 lumens flashlight to see anything (or lack of in this case). i just bought the motor so i dont really have any info. it runs, just doesnt idle like a johnny rude should. maybe its just the carb? compression is 110 in both holes, plenty of spark.
i dont think playing with the points is going to make a diff, as it seems (rough idle) is carb or vacum related. sorry about the spelling.
dino

 

[dkonrai]

Re: 72 20hp johnson idle needle too rich?

k..experiencing same symptoms with a '72, 25 hp...terrible idle and having to reset the idle mixture each time the engine was started cold. I found a nos needle on ebay which is different from the one presently installed. I can see that if the portion of the needle between the threads and the beginning of the taper < the "barrel" of the needle?> was too thick then the needle valve bearing couldn't compress enough to allow it to fit into the seat. If that's what you're experiencing, maybe this isn't the correct needle ? Has the engine ever idled well? As the 25 hp. I have sits now, I doubt it'd ever be "good" as a trolling motor.

that could be it, but the bearing wont fit no matter what. it seems the bearing is too large to fit in the carb threaded cavity.

 

[AlTn]

Re: 72 20hp johnson idle needle too rich?

k..well I used a pick to get the old bearing out too, but the bearing I got from the dealer just slipped over the needle and threaded back in along with the needle...a little tight but no more than you'd expect for something that is to seat and not come back out w/o some assistance...did you happen to look at how much of the needle taper, at 1 1/2 turns out from a soft seat, extended into the "well" < I don't know the proper term for it > that the core plug covers?

 

[dkonrai]

Re: 72 20hp johnson idle needle too rich?

here are some photos. the bearing doesnt fit (?) . i can see way down the body that there seems to be a collar that would accept a sleeve (bearing) but what is the stupid part number??? i ordered the part number listed but as you can see there is no way this is gonna fit.

dont know if this shows the carb body

when i pulled the needle this morning, i noticed it was only a 1/4 turn out. all of the other jonnyrude carbs i have worked on the 1 1/2 turn was always pretty close.
arrrggghhhh
dino

 

[AlTn]

Re: 72 20hp johnson idle needle too rich?

same part # for the bearing that I used on this '72-25 hp...I'd pop the core plug..#5 on the carb diagram..shine a light in, then look through the needle passage and see if there's a blockage of some sort, i.e..broken needle tip, piece of old bearing,etc...something must be funky/lunky somewhere in there...will the bearing fit w/o being on the needle and the needle retainer removed?

 

[dkonrai]

Re: 72 20hp johnson idle needle too rich?

got the needle bearing in , duuhh. all i had to do was push the plastic bearing in all the way. may have slightly damaged the bushing, but it works pretty good now.
vid

1972 johnson seahorse 20 hp runs pretty good. second round - YouTube

wish i new how to imbed.
dino

 

[AlTn]

Re: 72 20hp johnson idle needle too rich?

good deal...now to get some lube on that recoil spring..liberal dose of wd should help...spray,drain,pull the start rope a few times, repeat as necessary and, unless the spring is getting weak ,it should be much improved

 

[dkonrai]

Re: 72 20hp johnson idle needle too rich?

**update**
had some time and got the needle bearing i needed. bought them from a local shop. well original 20hp carb is shot (?) but the good news is that the used 25 hp i got from omcjoe, works pretty good. got the motor to finally idle.
my guess is there was something wrong with the original carb?
thanks for all the tips. i did recheck the points, and she was pretty darn close to .020 . immediate plans are to finally run the motor on the 14 foot duroboat. next is a reseal, then a full tune up.
thanks again!
dino