25 johnson 1990 idle/running troubles tried everything I can please help

[985johnm]

1990 25hp johnson J25RESB. From the beginning- motor began to run poorly after sitting up for a couple of months. I rebuilt the carb like I have done before, but without the aid of a mechanic friend I used to have. The carb was dirty and needed to be rebuilt. After the rebuild motor still ran poorly. The motor would only run top end if I pumped the ball to the fuel line, and would constantly surge. I bought a new fuel line, new tank, and rebuilt the fuel pump. Motor still runs poorly. I checked all vacuum hoses and no leaks replaced all fuel lines under the hood. I just checked an exploded diagram view of a carb and noticed a part numbered 22 on the diagram called a orifice plug. I don't remember the new kit coming with that and I don't think my bowl has one in it? Does anyone think it that could be the problem?

I also would like to know if anyone knows what is the optimum place the butterfly slide operator thing should be set? The upper portion of the motor rotates when the tiller handle is turned, this slides a roller and opens the carb butterfly. There is a small set of lines right of center on the rotating mass. Is this the base of a idle position?

please help all input is welcome.

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

well just took off the carb and looked in the bowl. I have a orifice plug safetly installed. Looks like I still can't figure out my problem. Oh and I tested the compression and both cyl. are around 115lbs.
please help john

 

[jbjennings]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

To me, it sounds like a possible bad fuel pump, or an improperly adjusted float. Could be any number of things, however. You may want to describe any and every single thing you've fiddled with in your work so far, so we can help you isolate the problem. It surges even when you pump the bulb constantly? If so, I'd say you still have something wrong in your carb.
Also, have you used a $6 spark tester at autozone to check to see that you're getting good, constant spark that will jump a 1/4" gap? If not, I'd do that as soon as possible.
Just some suggestions,
JBJ

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

things I've done:
-rebuilt carb
-rebuilt fuel pump
-all fuel lines replaced
-changed oil in lower unit (has nothng to do with problem but I did it)
-new gas tank
-compresson tested both cyl. are @115lbs
-new plugs
-new vacuum lines
-gently bottomed out needle valve screw and backed it out 1 and a 1/2 turns.
-1.motor starts easy but must idle high or it kills.
-2.motor eventually stalls out when I try to idle it down
-3. Idles really rough, it pops and snaps, whuuuuuuuuuun, snap, whuuuuuuun, snap, whuuuuuuuuuuun, die.
-soaked carb over night.
-still have the same problem.

 

[jbjennings]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

Sounds like a lean sneeze to me. You might try backing out the idle mixture screw so that it richens the mixture and it should stop sneezing on you. If adjusting the mixture screw doesn't have any effect on idle, then the idle circuit is clogged somewhere. Usually when you're adjusting the screw, if it's rich it will idle slower and as you lean out the mixture, you will hear it idle faster and faster until it gets too lean and it starts "sneezing" like it sounds yours is doing. I would expect 1 1/2 turns out would have it running rich. What procedure did you use to set the float? If it's too low it may make it run lean.

Also, you might spray a little WD-40 around the carb and intake manifold while it's running and if you spray it in a particular place and it stops sneezing and smooths out, you may have found a vacuum leak. I like to use a little propane torch to put propane gas around the carb sides and intake and see if that has an effect for the same reason.
It almost sounds like a vacuum leak leaning out your mixture, especially since you have the idle mixture needle 1 1/2 turns out and the carb. is clean.
Keep posting back-----you'll find the gremlin eventually.:redface:
JBJ

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

- I leveled the float level with the carb upside down.
- I soaked the carb overnight chemtool. sprayed it out with carb cleaner then compressed air.

 

[bktheking]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

things I've done:
-rebuilt carb

When you did this did you remove the welch plugs and let it soak and make sure the idle passages were free and clear of dirt? Sounds like the orifice is functioning as it will run off idle, i'm thinking it's still dirty, particularly on the idle side of things . Take it apart and inspect, check float for condition and installation the right way around, shake it to listen for fuel slosh (shouldn't have any), check float height- should be parallel to carb body, pop those plugs out while you are at it if you didn't already. Check to make sure the float isn't hung up in any way.

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

-this adds to previous list of stuff done to motor
-Brand new float
-float level with carb body
-I've cleaned it twice and it looks new, all the orifices flow great

-Which passage is responsible for low idle?

 

[elkhunter338]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

Have you tried fresh non-eth fuel. My 25hp johnson this summer would not start and ran poorly and it was the fuel. However the ethenal fuel was not that old 3 months with no stabilzer. Fresh fuel it ran great.

Also have you check to make sure the thermostate is letting the motor come up to temp. I have noticed if 2 stroke outboards run cold they do not run very well.

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

I have fresh none ethel fuel.

 

[Cofe]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

I have a similar motor that you have, and I have done the same things you have done so far.
The fuel pump is tricky to get together right and keep the diaphragm tight. Follow the directions that came with the kit. It took me two attempts to get mine right.
Also do a carb link and sync. The roller you are talking about sets between two marks on the plastic spark advance plate, when the motor is in idle position. The manual describes the proper link and sync technique. Hope this helps

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

--no directions came with my fuel pump. I think I did it right.
--thanks for the comment about the throttle markers.
--I don't have a manual, I set the roller between the two marks, the butterfly is completely closed, then when the tiller is turned all the way open I set the buttlerfly all the way open.

tell me if this is right.

 

[bktheking]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

--no directions came with my fuel pump. I think I did it right.
.

If you didn't it wouldn't run at all. As for low idle, I believe there is a welch plug on the top of that carb that covers the idle ports.

 

[Cofe]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

--no directions came with my fuel pump. I think I did it right.
--thanks for the comment about the throttle markers.
--I don't have a manual, I set the roller between the two marks, the butterfly is completely closed, then when the tiller is turned all the way open I set the buttlerfly all the way open.

tell me if this is right.

Yes that is the correct way to set the carb.

I would recommend getting an OEM manual. It will save you lots of headaches.

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

what is the best johnson manual for the price?

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

Soaked carb overnight after taking all the aluminum and lead plugs out of it.
I bought another carb kit from napa, who had three in stock! Then I cut open a number three 20gauge buck shot and used the lead shot and a punch to seat the lead.
Everything is back together and the throttle linkage is set. The boat cranks easier and is idling a little high. It seams like it likes this. I think my set screw is at around 2.75 turns out.
Please tell me the most cost effective good manual to get.
thanks john

 

[psteurer]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

The best would be the Original Equipment Manual from OMC for 1990. I bought mine on eBay for $25. Type in Evinrude manual 1990 into ebay and you will see one for $39 right now. If you wait, you might find one cheaper. With just a little mechanical ability and this manual, you can fix just about any of the more common problems and also some of the more uncommon ones.

 

[jbjennings]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

You want to be careful it's not idling too high or it will eat your clutch dogs over time when you shift gears. If it's too high, it's either still too lean or your idle stop needs to be reset to let it idle a little lower. It seems like something is going on for the idle mixture to need to be out that far, but whatever works.....
Just an idea,
JBJ​

 

[985johnm]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

what does the bolt in the center of the front, way in the back under everything, control? Is this how you make the motor harder to turn?

My carb is idling great now and it's about 2.25 turns.

 

[bktheking]

Re: 25 johnson 1990 idle/running troubles tried everything I can please help

Number 65? Co-pilot adjustment screw, control's how loose or tight on the swivel of the motor. Can't see anything else on the diagram with a screw or a spring that would do this.


Glad to hear it's idling now.