1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

[Br1dgemann]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

j_k_

Just curious - what year, model and horsepower are you working on?

 

[jeffersondodson561]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

I have to run my carbs at 7-8 turns out on the idle mix screws. That is near the end of the spring friction point.

I think your mixture screw is metering air insted of fuel.

 

[jeffersondodson561]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Jonesg...I have pressed the key in at the dead spot to inject extra fuel, also tried squeezing the primer bulb to see if it is a fuel pump suction issue, no change.

What happened when you pressed in the enrichener? Did rpm drop at all? Is the red valve broken, common on OMC's. If this is working you should have noticed some sort of change in RPM's. Is it at 6 oclock in relation to the solenoid. Follow the lines from the enrichener to the manifold, also check that the nipples on the enrichener are not broken causing a lean condition.

 

[Br1dgemann]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

jeffersondodson561,

Squeezed the primer bulb - no change in behaviour.

Pushed the choke in - RPM drop but problem persisted.

Solenoid valve is pointed to 6 o'clock position. I performed a cursory check of the solenoid - did not feel any fuel leaking after I squeezed the primer bulb. I will look at it a little closer tonight after work.

 

[jeffersondodson561]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

One thing I have noticed about these "plastic" carbs is that over time they can warp. One problem I have run into is the bowl. You need a perfectly flat surface, at our shop we had a 18"x18" piece of slate. If you take the carb bowl off and rub the contact surface in a figure 8 motion on a piece of 220 grit sand paper lightly and look at the wear pattern (maybe a kitchen counter top will work). May sure that the emulsion (rough surface caused by the sandpaper) is evenly distributed over all the contact surface of the carb bowl contact area. If you see that contact area is warped, gently sand it down until all areas look the same. This is a thought but if you have not rebuilt the carbs I would do that first.

 

[Br1dgemann]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

jeffersondodson561

I already rebuilt the carbs (several posts up), but can see how easily the bowls can warp. They are very sensitive to overtightening just one of the screws. When I re-installed the carbs on the engine and finished hooking up the fuel lines, I was very careful to check around the perimeter of each bowl to make sure that there were no leaks at the gasket area after squeezing the primer bulb. As murphy's law would have it, I had one bowl that was leaky and had to be "tweeked" in a similar fashion you mentioned after playing with the screws would not correct it (granite countertops are the bomb!).

Anyhow, going to run a different, known good timer base tonight and see if there is any change with respect to my original problem....

 

[jeffersondodson561]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Just don't let the wife see...

 

[jonesg]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

So , ? did the timer base help?

 

[jonesg]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

The motor is sensitive to trim angles, .

Thats a sign of something going on, I was reading about it recently but can't recall where I read it.
I think it had something to do with a twisted float tab in the carb bowl.

 

[Br1dgemann]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

jonesg,

Nope, the timer base did not help one bit. So, I was really irritated and did the following:

Took the air silencer/air box off the engine and ran it at approximately 2000-2200 rpm, which right where the problem starts. Put my hand in front of each carb about an inch away and had a couple of them spraying a mist of fuel out at me. I also thought I felt air blowing out at me. So, I might look into the reed valves.

Like I asked a couple posts up, I was curious if there were other symptoms of bad reed valves beside spraying fuel at idle...because my engine idles fine. But since I have eleminated every electrical component in the ignition system, already rebuilt the carbs, and performed a link and sync, I might as well tear into it a little deeper.

 

[daselbee]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Not the reeds. You have 6 reed blocks, and I THINK they are 5 petal reeds, so how could 30 of those things be bad to the point of causing this problem. And how could they be bad on my motor too....

Not the reeds...

EDIT: I pulled a mechanical!!! I have a crack in the fiberglass around my transom, so the boat is down for the count. I hope to have it running in about two weeks. Sorry I will not be able to test/try/assist on this problem.

What happened to FAZT? He posted once...

 

[Br1dgemann]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

daselbee,

That is why I asked about other symptoms for bad reeds several posts back. I also said the issue showed up on 2 of my carbs. I assume all it takes is one reed petal out of the block of 5 behind each carb to be bad to start causing problems. The reeds are supposed to keep the air and fuel from spitting back out the carb, right? So, theoretically if one petal is bent, or cracked, or broken and can not seal properly, there is going to be some type of blow-back.

I am open for any other thoughts on the matter.... Also willing to entertain any other potential ideas because I am pretty much at my wits end.

Sure hope you are able to fix that transom crack soon. Glad that you found it before something serious happened. Let us know how the repair goes.

 

[jeffersondodson561]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

...I replaced the magnet and checked that all the other ones were properly attached and located.

Sorry I didn't read your dissertation earlier until now, DID YOU VERIFIY THE POLARITY OF THE MAGNET BEFORE INSTALLING IT ON THE FLYWHEEL?

 

[daselbee]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Bridge...

I believe that a very small amount of misting back out of the carbs at all rpms is normal.
I have had a reed block gasket "squirm and walk" because of poor adhesive, and open up a gap along the long side of the reed block and the metal seating surface of the intake. The result was not subtle. There was MASSIVE blowback out the one carb that had the reed block leak. MASSIVE.

I had #6 once that was not sync'ed correctly with the other 5 and it caused poor idle, and blowing back out the carb. Sync'ed them up, and still very very minor misting back, but the idle was fixed.


I just do not think the reeds are an issue with our motors. Have you tried hotter plugs?

 

[Big flop]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

While you were running in the troubled area with
the air box off did you try any previously mentioned tricks?
tooth pick in air jet, it will richen intermediate circuit.
Or spray bottle of gas/oil into each throat
Pushing in the choke will richen the hole motor and
I think you need to do your check one carb at a time.
Even each plug wire off one at a time,
this may help to isolate it to one cylinder???

 

[Br1dgemann]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Sorry I didn't read your dissertation earlier until now, DID YOU VERIFIY THE POLARITY OF THE MAGNET BEFORE INSTALLING IT ON THE FLYWHEEL?

Yes, I did. the magnets have one corner different than the other 3 and that identifies which way the magnet is to be installed.



Big Flop,

When I was running the engine without the air cover, I was not totally prepared to troubleshoot further, it was a move of desparation. I did push in the choke. As before, it dropped the rpms but did not clear it up.

I actually completely blocked the intermediate orifice of the two carbs that were misting. It did not change anything.

I did not have a squirt bottle with me and it was a bit choppy to be hanging off the boat to pull plug wires.

I guess I will make one last try with the following: tooth picks for the air bleeds and a squirt bottle of pre-mix. I will also need to try to pull plug wires. I will try to make that run this week, weather permitting, and post an update.



Daselbee,

Your observation has been heeded. I will hold off on tearing anything else apart until I try what I mentioned above. Last run out, after changing the timer base, I put brand new QL87YC plugs in her.

 

[jeffersondodson561]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Yes, I did. the magnets have one corner different than the other 3 and that identifies which way the magnet is to be installed.

I am curious, where did you find the 1 magnet? I have looked at the fiche and don't see where you can buy just one?

http://shop2.evinrude.com/Index.aspx?s1=jr0pcfji7sut7vlem0u7d252c6&catalog_id=0&siteid=1

 

[Big flop]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Try the toothpick test one at a time. Once you insert it,
within few seconds you should hear a change, if it slows
down remove it and move to the next. If it improves and
continues to run good with the toothpick in it leave it in
and move to the next carb.
You may hear a quick improvement But then it slows down
because of the rich condition from blocking the air.
Listen very closely for changes
hopefully it will give you a answer, is is it gas related.
Be careful with spark plugs, OMC went
to a hotter plug than the QL78YC and resulted
with power head problems

 

[Br1dgemann]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

Try the toothpick test one at a time. Once you insert it,
within few seconds you should hear a change, if it slows
down remove it and move to the next. If it improves and
continues to run good with the toothpick in it leave it in
and move to the next carb.
You may hear a quick improvement But then it slows down
because of the rich condition from blocking the air.
Listen very closely for changes
hopefully it will give you a answer, is is it gas related.
Be careful with spark plugs, OMC went
to a hotter plug than the QL78YC and resulted
with power head problems

Will do. Patience will be the key with this. I will also go back to the QL78YC plugs so I do not give myself any more problems.

Keep ya posted!!

 

[jonesg]

Re: 1999 Johnson 250 has a ?dead spot? between 2000 and 3500-3600 RPM

I would consider reeds in the list of possibilties, it don't cost a fortune to look them over.
Also came across this, not sure if it applies to yours.
http://www.bbcboards.net/zerothread?id=665325

Use a timing to test ignition on the water instead of trying to pull plug wires.