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

[daselbee]

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

Bridge....I have an engine doing the same thing. (I think).

It is a 1996 225.

Mine will begin to "stutter and miss" at around 2000 rpm, and continue this up thru about 3500, where it smoothes out.

Two things I have noticed...One is that the plugs are carbon black fouled, but not so bad that they require changing. I have changed them to new plugs, no difference tho. They are not nice brown tan like they are supposed to be.
Second, this motor will not wind up to 5500. max I can get out of it is about 4800.

Many trials, new PP, new timer base, different flywheels, timing light on all plug wires when stuttering, press key in when stuttering, all that stuff...none of it has any effect. Compression is 100 all around, carbs are spotless, and link and sync is perfect. Carbs are stock jetted. So I am fighting this also.

All this on the same boat, same loaded weight, same prop, etc. that it was running when if would flat out scream down the water.

So I ask...does yours wind up to full rpm? And what are your plugs looking like?

And, yes, that nipple in the center of the intake is capped with a rubber cap. No hoses on that one.

 

[Br1dgemann]

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

Daselbee,

I ran it at WOT for a short period on Saturday. Only saw 5100-5200 rpm whereas it turned 5600-5700 rpm in the past. Same hull, same loading condition, and same prop.

I also did the timing light check to see if I was dropping a cylinder but was not. My plugs are sooty, carbon black like you not enough to warrant changing...but to be honest, I do not remember my plugs ever being a nice brown color - always black.

I checked compression in February and was reading 105-110 on the cylinders. I can check again tonight after work, although I have not subjected the engine to any trauma (ie: no "no oil" warnings).

I was thinking about ordering a timer base, though I am a bit wary now since you did not have success with changing yours - did you get an Johnrude brand or a CDI brand?

Hopefully we can work together and brainstorm the problem so we both can get back to enjoying our boats. I will post back the results of my compression check later tonight or tomorrow morning.

BTW, I put a new vaccuum cap on that nipple prior to going out Saturday

 

[daselbee]

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

I am fairly well convinced that we have the same problem.
I did not buy a new timer base, I used three that I have from used motors. They all performed the same.
Same testing with the powerpacks and stators I tried.
No new ones, but so many used ones to try from; they all performed the same.
I have measured DVA voltages all thru the ignition system...all OK. DVA at the orange primary wires is 190v. One was down at 160v, but that was a bad coil, and is now fixed. I really thought I found it with that, but no.

My spark jumps 7/16" easily..hot blue snap.

So, black sooty plugs says weak ignition or over rich mixture to me. But how to lean out the carbs? This seems to be a midrange issue, but our carbs only have idle screw mixture adjustments, and leaning out the high speed jet with smaller jets will affect other speeds...
I can try it though. I am running 72Ds right now, maybe 70Ds or 68Ds.....

Or maybe hotter plugs. I have the QL78YCs now. I do have some QL87YCs (much hotter) that I could try just to see if anything changes.

I have not verified...but the plug wires...what affect would wrong plug wires have. I refer to the copper conductor vs the resistor wires type....

Anyone know? Anyone know how to tell what type of wire is in use now?

 

[Br1dgemann]

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

I believe we have copper conductor wires. I am not sure what would happen if the other type are used. I do know if a resistor plug is used instead of a Champion "Q" series plug, you can get poor performance. I would not believe it if I hadn't run NGK plugs in a pinch one time and noticed a totally different running engine compared to a Champion plug.

Our carbs have an intermediate speed air orifice. It works opposite of a jet. You could go to a smaller orifice to richen the mixture up. Your carb should have a # 30 orifice. You could go down to a 29 or 28 orifice to richen it up or go up to a 31-32 orifice to lean it out. The orifice looks like a jet and it is located just above the idle mixture screw. I don't think we want to change a high speed jet - too risky if the engine goes lean.

I was thinking about trying QL82yc or QL87yc plugs and see if that makes a difference. If you try it, let me know how it works.

 

[daselbee]

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

Bridge.....that #30 orifice is the idle air bleed. That is the description in the parts listing. I have experimented heavily with that particular orifice and I can only determine that it affects the idle mixture. One size bigger equates to one turn IN on the idle mix screw.

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. So, if you go up to a 33in the idle air bleed orifice, you can turn the screws back IN to about 4-5 turns for smooth idle. Makes the spring tighter.

Older model carbs had two air bleed orifices in the same location, one was idle air, the other intermediate air bleed. They changed the orifice sizes extensively from say 1989 thru 1994-1995, and finally settled on a carb with one idle air bleed orifice.

But no matter, right at this moment I have the stock #30s in and i still have this stuttering issue going on.

 

[j_k_bisson]

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

Hey guys, sorry to but into you conversation. Question for you. Is this shutter you talk about between say 1200 rpms to 2200 rpms? I am experiencing this also and was thinking that the motor is loading with fuel with idling for so long when warm. I though it could possibly be the recirc line I used when I replumbed the motor. I was looking at the line tonight and it is 1/16" line id. The book calls for 1/8" id line for checking them with a syring. I was thinking it could be the smaller id was causing the recir system not to work properly. Higher vacuum would be needed to draw the unused fuel through the smaller lines due to ID restriction. Could this same thing be happening with your motors? Something due to Ethenol colapsing the inside of the lines over time. Sort of like a brake flex line? Just a thought.

Sorry if my thoghts are a bit of the board. This shutter is driving me crazy. Or is it normal with these motors? I do have the fixed jetting carb unlike you guys.

 

[Br1dgemann]

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

daselbee,

The shop manual calls them an intermediate orifice, and the parts diagragm calls them an idle orifice....I guess you already exhausted that option.

I checked compression last night and got the following:
1- 110 psi 2- 105 psi
3- 115 psi 4- 110 psi
5- 110 psi 6- 105 psi

So it looks like compression is good. I still might try a timer base. I also looked at the plugs. Attached is a pic of what they are typically looking like.


j_k_bisson,

I appreciate the suggestion. Our shutter/bog/ problem exists between 2000 rpm and 3500-3600 rpm. I may look to see if there are any blockages in the recirc system. I did not explore that element in any depth because the manual says when there are recirculating problems, the engine becomes very sensitive to trim position and my engine does not care if it is trimmed in all the way or out.

 

[jonesg]

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

What about this, its breaking up at a certain rpm but you can't say with certainty if its fuel or ignition related.
Try running it in the dead zone and spray fuel into the carbs from a spritzer bottle.
Try running it with the shift assist unhooked.

 

[j_k_bisson]

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

Shift assist? That could be causing this. How so?

My plugs look the same after 1.5hrs.



Unfortunately my shuddering is not in the range you are talking about. I did not know that about the Recirc and trim. I'll try that next time out. Thanks!

 

[Faztbullet]

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

Found a nipple between the throttle bodies with a vacuum cap that was cracked/ split all to hell. Attached is a picture with my finger pointing to the location. What is this for?? and why was it (sort of) capped??

This intake is used on the V-4 looper also and that nipple was for the air box drain. Are you testing this with the air box on or off???

 

[daselbee]

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

Hmmm....a lot to think about here.
I figured (I guess incorrectly) that my experimentation with the jet sizes/ vs. the idle screw settings was showing me that those air bleeds were for idle only. I am re-thinking this. It appears that all the circuits - idle, intermediate, and high speed have more of an overlap of function than I first thought.

As a test, I am going to plug the int air bleeds with toothpicks just to see the effect. Not as a permanent fix...I just want to see what happens. If it bogs more thru the intermediate dead spot, it is richer due to the air bleed being closed. If it is indeed rich causing this problem, I will try 36s in the int air bleed position. But that will definitely screw up the idle screw settings..they will have to be more open, and will be way out past 7-8 turns. This is getting tricky.

Jonesg...I have pressed the key in at the dead spot to inject extra fuel that way, no change.

Fazt...yes the air box is ON for my testing.

Regarding the plug pictures, mine are a bit blacker and sootier. But not much.
I am also going to try the QL87YC hotter plugs. I am going to skip a range and go all the way to 87YCs. If it changes anything, I want it to be a noticible change, not something that I will wonder...hey is this better or not?

If I have to adjust plugs down to the 82YCs after reading them, then I will.

On an aside....I blame all this on ethanol. Not because of the affect it has on the rubber lines, etc., but because it has more oxygen molecules in it than straight gas. Alcohol is an "oxygenating" agent in gas when used as an additive. So I figured it was running lean simply because there was more oxygen molecules in the fuel. Is there any merit to this? Opinions please.

EDIT: "running lean at idle" in the above line. That's why I had to open the idle screws up 2-3 turns to get rid of lean sneezing. This is only at idle. And on thinking a bit more, this DOES NOT go with the rich, sooty looking plugs....SO,


http://www.ethanol-information.com/ethanol-glossary.php
■Oxygenated Fuels:
A fuel such as ethanol-blended gasoline that contains high oxygen content is called "oxygenated." Ethanol is an oxygenate, meaning that it adds oxygen to the fuel mixture. More oxygen helps the fuel burn more completely, thereby reducing the amount of harmful emissions from the tailpipe.

 

[Br1dgemann]

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

Fazt...my air box is also ON for my testing.

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.

jonesg...I have already disconnected the shift switch to see if it was grounding out the cylinder bank. No change - re-connected it. I also tried disconnecting the S.L.O.W. function into the power pack - actually both power packs I have tried. No change - reconnected it.

I would like to try spritzing fuel down the carb's throat, but I thought the air box is supposed to be on when your are running under load.

 

[Br1dgemann]

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

daselbee,

Any progress on your end?

 

[daselbee]

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

No, sorry Bridge...Gotta get to the water. I will be sure to post ASAP.

 

[Br1dgemann]

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

daselbee,

I started swapping timer bases last night, just to completely eliminate every single ignition component ( and I wouldn't know what to do with myself if I wasn't outside cussin' this damn engine ). While I had the flywheel off, I started wondering - Reed Valves?

Everyone says the common symptom of bad reed valves is that fuel spits out the carb. But is that THE symptom or could there be more subtle ones that do not necessarily spit fuel out? The shop manual indicates if you lose WOT RPM, one of the things to look at are the reed valves (actually, the manual calls them leaf valves).

Thoughts?? Anyone??

 

[j_k_bisson]

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

I do have a bit of progress report. I stopped by my local dealer and looked into the proper Recirc lines ID. The proper fo these motors is 1/8" ID. I used 1/16" ID when I redid the system. They stated that this should not be an issue though. My thoughts are first off the vaccum difference required to draw the same amount of fuel through the smaller ID hose. But the other one is weather the smaller ID hoes will evacuate enought fuel to keep up with the engine so this do not over load.

Anythoughts on this. They stated that these motor do have a tendancy to load up with fuel. This is because the jets that Evinrude uses are larger to bridge the gap/transision moving up between jet sizes. Makes sense. My problem is if I intend to travel/drive at this intermediate speed 12-22mph do I change props, down a pitch, or do I change jets?

 

[Br1dgemann]

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

j_k_bisson,

You were actually able to get the 1/16 id hose onto the recirc hose barbs?

In your earlier post you said the speed was 1200 to 2200 RPM, in your most recent post you said 12-22 mph. Just curious which it is or is it both because of the hull and prop?

I would think that rejetting might turn into a POA because of the overlapping that daselbee talked about a few posts up.

On a different note, if the smaller diameter hoses can not remove the excess fuel in your engine, you should experience symptoms similar to a blocked recirc system - the engine should become sensitive to trim angles while idling and the bottom plugs should foul up. Are you experiencing these issues? If not, I would think the recirc system is ok.

Just my $0.02.

 

[j_k_bisson]

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

Yep you would be suprised at what I can get on what when I want to. Just need a bit of lub! lol But yes the hose line was very plyable.

The speed and RPM are the same. It's due to the hull/prop configuration.

POA? Not fimiliar with term.

The boat idles great, no kicking or sneezing. Bottom plugs are not fouling up even with double oil mix. The motor is sensitive to trim angles, but the boat is not up on plane durning this perriod. I need to keep the rpms above 3200rpm to maintain plane.

 

[Br1dgemann]

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

Oops, meant PIA, not POA. Pain In the A#@...

So, the motor is sensitive to trim angles, just not at idle speeds? And the plugs are not fouling? Then according to the 'ole OMC shop manual, you should not have a recirc problem.

Which leads to the question - re-jet or re-prop. Re-prop sure sounds easier to try.

 

[j_k_bisson]

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

I'm thinking so to. I'm not looing for top end speed. 45 mph in 4-5 ft waves is not the most comfortable ride. I rather low end torque and crusing speed.

What is a decent cruising rpm I should be shooting for with this motor?