Idle mixture screw out 7 turns not 1 1/2

[tfbrown1270]

My 1994 Evinrude 20 hp was running well till I decided I should adjust the mixture screw.
I discovered the following as I progressed..
-When I turned the screw in to the stop BY HAND to see where I was starting from it went in 3 1/2 turns.
I removed it to clean it and shoot some deep creep in the hole,
-When I put it back in I retightened it by hand then backed out 3 1/2 turns (should have been where I started),....ran awful, sounded wierd and didn't smoke much. I had to back it out another 3 turns to keep it running..
-After I reseated the needle by hand I found it would go in further with the help of a screwdriver, not turning hard or anything like that just till it was seated.
Then I backed out the recommended 1 1/2 turns and it wouldn't even start..
I ended up backing out 7 turns from seated (with a screwdriver) till it was running reasonably smooth again.

Clearly I should have left well enough alone.

Anyway..since I did what I did...

-Can I hurt the motor by running it with the needle set that far out?
-Which way was right..set the needle by hand or with a screwdriver?
-What next?

Thanks for all the help...

 

[Mas]

Re: Idle mixture screw out 7 turns not 1 1/2

I'll be looking for the "big fish" to reply to this one...a

I've got the exact same motor & year. I messed with the idle mixture screw because of too much smoke at idle. I too was about 7 turns out, but clearly too far out. The tension spring seemed to have little effect at that point. I think that motor vibrations made the screw wiggle out further than need be??

My motor will not even start at 1 1/2 turns, as many have recommended. I can get it to burp & sputter at about 3 turns.

One question I have is "What is lightly seated?" The tension spring must be fully compressed to be lightly seated...correct?

I'm currently out about 4 1/4 turns. The smoking has decreased dramatically, but now I'm worried about running too lean & overheating at idle. I'm looking to buy some Thermomelt Sticks to check idle temp.

I've ordered the factory OMC manual to see if this is an odd year for carb tuning...or is something else wrong with my seeming great motor with lots of power...this doesn't make sense!

Certainly I'm no help...but at least I can say I'm there with you!

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

Great to hear I'm not the only one (misery likes company)...I'm going to try the adjustment without the spring tomorrow to see where this mysterious lightly seated position is as I believe the spring is messing up the process....

 

[Mas]

Re: Idle mixture screw out 7 turns not 1 1/2

Without the spring, I'm sure you'll be way too far in & will damage the screw/valve....be wary!

Did your motor smoke excessively prior to "tuning?" Especially at low speeds/idle??

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

Smokes like I own an oil well....less so after the decarb but still more than I think it should...at idle (on the muffs) the smokes not too bad but in gear at moderate throttle (no tach) it pours the smoke out....holy mosquito fogger batman!

 

[ob]

Re: Idle mixture screw out 7 turns not 1 1/2

Lightly seated simply implies to not torque down on the screw so tight as to distort or cut in to the needle seat.With that said,each engine will have it's own "sweet spot" so to speak as to the final screw setting.Bare in mind that sometimes there is gummy residue that can build up within the idle circuit porting that will require a more open position of the mix screw to compensate.Particularly if the engine has set out of use for a spell.If you have to back out on the idle mix screw so far that the spring no longer has any preload,I suspect that the carb porting may need to be cleaned out.Just shooting cleaning fluid through the orifices or porting doesn't always do the trick.Dismantling ,soaking ,and clearing of the orifices and porting with indexed torch tip cleaners or similar tool does a good job.

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

I noted a few bubbles coming out of the gas line hose to barb connection at the tank so I replaced the clamp, with that and a few minutes finding "the sweet spot" I managed to keep the motor running. I also mixed some new fuel/oil at 50:1 just to make sure it was right, I thought I might have a too much oil situation since it blows alot of smoke, especially at moderate throtrtle, the smoke at idle doesn't seem bad now.
As a matter of fact despite the cold (-1 c) I had to use the emergency stop pull cord to shut it down because it wouldn't quit.......I was very pleased with that d.
It seems to idle pretty slow too...not smooth like a 4 stroke or anything but pretty good...can anyone advise how I can fiqure out how fast its turning...I quess I'm asking if there is a good tach for this little motor; keeping in mind there is no console to mount one on, this is a sit at the back and steer motor.....thanks again all

 

[OBJ]

Re: Idle mixture screw out 7 turns not 1 1/2

Yes there is a good tach....It's called a tiny tach. Allows you to monitor the engines rpm wether it's a rope or electric start.

Let me add some confusion factors to the situation.

First, the sync between the cam and cam follower roller must be right for the engine to idle correctly. Look to the upper right of the carb as you are looking at it from the front. You should see a roller on a stem that will ride against the cam just under the flywheel.

On the cam you should see a single reference line and in some applications two.

When the cam roller is centered (on a single reference mark) or centered between two reference marks, the carbs throttle plate should just start to move toward the open position. There is a throttle lever screw on the carb to make any adjustments needed. Just look on the strarboard side of the carb where the cam link connects to the carb lever.

Second confusion factor.....the carbs idle circuit.

Your carbs us an idle lift tube to get the fuel up to the carb idle circuit. The hole at the bottom of the well tube is small......as in sm.....allll. It can be restricted with the smallest of debris.

7+ turns out is a lot. Getting the engine to idle as I recall should not take any more than two to three turns out on the low end needle and adjust low end idle with the engine warm, on the boat and in the water under way. As ob posted, not all engines will have the same setting on the needle. So, final adjustment will depend on your particular engine.

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

First, the sync between the cam and cam follower roller must be right for the engine to idle correctly. Look to the upper right of the carb as you are looking at it from the front. You should see a roller on a stem that will ride against the cam just under the flywheel.

On the cam you should see a single reference line and in some applications two.

When the cam roller is centered (on a single reference mark) or centered between two reference marks, the carbs throttle plate should just start to move toward the open position. There is a throttle lever screw on the carb to make any adjustments needed. Just look on the strarboard side of the carb where the cam link connects to the carb lever.

Hummmm...I checked on mine it has two lines about 1/8" apart (on the horizontal plastic part under the flywheel right above the carb that rotates as you apply throttle),
when the hand throttle is turned to the lowest/slowest setting the roller is about a inch to the right (when viewed from the front of the engine lloking back at it) of the double lines,
as I advance the throttle the roller pushes the throttle open BEFORE I get to the double lines if you know what I mean.....
if this is too early and it sounds like it is...how do I fix it please....

 

[R.Johnson]

Re: Idle mixture screw out 7 turns not 1 1/2

The throttle plate should open beween the cam marks..to early is the better way to go, The the engine willi idle the best with the throttle plate completely closed. If the engine idle's with the needle turned out to far, {2 1/2 turn's off the seat} You have a restricted idle passage, or a vacuam leak. That engine will never idle properly with either. A early throttle plate opening will act just like a vacuam leak, but much exagerated., because that is what it is.

 

[Silvertip]

Re: Idle mixture screw out 7 turns not 1 1/2

Rather than have us type a very long link & sync procedure, do yourself a favor and buy a service manual that contains this procedure. Factory manuals are best and will save you time, money, and frustration. And it may even prevent you from destroying a perfectly good engine by doing something -- well you know what I mean. d

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

[I am learning a lot about the motor, I went out to the garage and adjusted the link so it "starts" to move the throttle plate when it gets to the double marks, I noticed a bit of slop in the links and plastic parts so I took that into account. The throttle plate begins to rotate at the moment the little roller hits the centre of the two marks...
I'm going to try and post a picture to see if it helps...the idle screw is the one at the back left of the carb in the picture, thats the one thats currently about 7 turns out from seated lightly with the screwdriver....or about 3 1/2 out from seated with bare fingers...maybe someone could tell me what the big screw is on the front of the carb (top), is that another adjustmnent?....ps I'm waiting for a manual I bought from E-Bay...

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

Oh Oh..I don't see it and I followed the instructions on posting a pic?:'(

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

I'll try again..its just 87kb..so its a small file on my desktop?

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

trying againhttp://s130.photobucket.com/albums/p243/wgg490/?sc=1&addtype=local

 

[Vic.S]

Re: Idle mixture screw out 7 turns not 1 1/2

To post an image from Photobucket just copy and paste the whole of the third line, labelled IMG, from the box below the thumb nail. (click on it to select it, then right click on it then copy)

 

[R.Johnson]

Re: Idle mixture screw out 7 turns not 1 1/2

That screw is nothing but a seal to the idle passage. If you remove it, you will find a red nylon sealing washer, It is not an adjusting screw.

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

The throttle plate should open beween the cam marks..to early is the better way to go, The the engine willi idle the best with the throttle plate completely closed. If the engine idle's with the needle turned out to far, {2 1/2 turn's off the seat} You have a restricted idle passage, or a vacuam leak. That engine will never idle properly with either. A early throttle plate opening will act just like a vacuam leak, but much exagerated., because that is what it is.

I cleaned the carb and set the float level, it was a little low and was letting some fuel through all the time...(I saw there was a little fuel running forward out of the carb, like a kid with a runny nose; I thought they all did that!), the float adjustment took care of that, I also set the timing roller to start to move the throttle plate as it gets to the double marks on the timing cam,

interestingly after I cleaned up the carb (it looked spotless but I guess it wasn't) I tried the mixture started at 1 1/2 turns from lightly seated, and lo and behold it started, I had to fiddle a bit but it ended up about 2 turns out running great not 7 turns d

Thank you everyone your help got me through...if I were to pass on any advice to others in a somilar situation (carb not working right) I would suggest a complete teardown of the carb, meticulous cleaning, clamp every connection to prevent air leaks and careful setup of the float and timing. Thanks once again..I'm sure I'll have more questions over the winter since I'm repowering my 16 ft Princecraft with a 1992 Johnson 90 hp VRO model.

 

[Mas]

Re: Idle mixture screw out 7 turns not 1 1/2

Well, sounds like a happy ending. I think I too will do a rebuild...being that I'm also way out of whack on my idle screw. I just got my manual yesterday. And yes, the factory OMC manual is the way to go!!

Does it still smoke @ mid throttle?

 

[tfbrown1270]

Re: Idle mixture screw out 7 turns not 1 1/2

definately still smokes at mid throttle, certainly not as much as before the work though. I am thinking smoke is inevitible with two strokes, I will be changing the thermostat in the spring in the hope I can bring the temps up a bit, that may make it more efficient.