Force 125 shakes at low RPM

A

auchandler1

Seaman Apprentice
Joined
May 27, 2011
Messages
41
Hey guys,
My force 125 shakes when it is in gear at low RPM's (1000-2000). When going faster and higher RPM's it smoothes out.

Whats going on?
Is it carbs or what?
 
B

bentle

Chief Petty Officer
Joined
Aug 2, 2011
Messages
492
Re: Force 125 shakes at low RPM

What shape is the prop in?
May want to pull the lower off and inspect the drive shaft and coupler for excessive play
and check drive shaft for straitness.
Do a compression & spark test on all cylinders. You may have one or more cylinders with weak or no spark & or low compression.
 
F

foodfisher

Captain
Joined
Feb 18, 2009
Messages
3,756
Re: Force 125 shakes at low RPM

Mine does the same. Just power through it. I asked the question and was told it's nature of the beast. No probs as long as I don't use that RPM. It's not a convenient speed anyway.
 
jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,969
Re: Force 125 shakes at low RPM

The air screws might need to be re-set.
Turn in till they just bottom out.GENTLY!!!
Then out 1 and 1/16th turn out.
The go for a ride or tie it to a pier,has to be in the water.Engine warm,in gear,idle 750-800.
The turn the air screws in slowly.When it bucks/coughs,stutters or stalls turn it out 1/2 turn.
Then do the other carb.
I usually do it two times.
Make sure the timing is right and when your done the RPM's are 750-800 in gear.
Any lower and it can stall.J
 
A

auchandler1

Seaman Apprentice
Joined
May 27, 2011
Messages
41
Re: Force 125 shakes at low RPM

When you said air screw do you mean idle mixture screw?

What kind of damage would I be looking at if running this for a while?
 
B

bentle

Chief Petty Officer
Joined
Aug 2, 2011
Messages
492
Re: Force 125 shakes at low RPM

Yes the air screws are the idle mix screws, both mean the same.
If the motor is running to rich then spark plug fowling will happen, over time the rings on the pistons will become sticky due to carbon build up and then you will have compression issues,
and cylinder wall damage. If running to lean then cylinder wall damage from broken and worn rings burned pistons and crank shaft bearing damage.
A bent drive shaft( not likely )can cause bearing and seal damage on the crank shaft and lower gear housing. A damaged prop cas cause prop shaft seal and bearing damage and eventually gear damage.

These are all possibilities but it may very well just be a force 125 flaw and something to live with.
 
B

bentle

Chief Petty Officer
Joined
Aug 2, 2011
Messages
492
Re: Force 125 shakes at low RPM

Does your motor spit cough backfire and die when at idle or just before putting it in gear?
At wot is there any bogging down or any kind of a miss while running at wot?
 
A

auchandler1

Seaman Apprentice
Joined
May 27, 2011
Messages
41
Re: Force 125 shakes at low RPM

At idle it is fine. I mean sometimes it just dies but nothing sounds wrong with the motor. I just figured it was carb issue with that. Putting it into gear and sometimes she dies. I have to give it some gas and rev it up then all is good but when I start giving gas it shakes and then when I get it up more with speed she doesn't shake anymore. Shakes only at low RPM's and she doesn't backfire or spit and has good water coming out the pee hole.
 
A

auchandler1

Seaman Apprentice
Joined
May 27, 2011
Messages
41
Re: Force 125 shakes at low RPM

Found this on Seloc Online Manual:

full_11002p102.jpg


1.Remove engine cover to gain access to carburetors and link rods.


2.Set idle mixture screw to proper base setting as listed in the Carburetor Specifications chart.


3.Install a flushing device or submerse lower unit in water.


4.Run engine until it has reached operating temperature.


5.Idle engine and adjust the idle mixture screw as follows:
◦Turn screw clockwise 1/8 turn at a time until the engine speed increases and then starts to sneeze or run lean.
◦Then turn the mixture screw counter clockwise 1/8 turn at a time until the engine speed starts to decrease or run too rich.
◦Calculate the total number of turns between the rich and lean settings and set the mixture screw half way or in the middle of the range. Repeat this procedure for all carburetors.

6.Adjust the idle screw to the proper idle speed as listed in the Tune-Up Specifications chart.


7.Stop the engine.
 
B

bentle

Chief Petty Officer
Joined
Aug 2, 2011
Messages
492
Re: Force 125 shakes at low RPM

Sounds good but really should be adjusted while in the water to set idle mix screws and tied
To the dock if doing it alone. If two of you and a calm day then out on the water is fine also.
Take a look at the sticky at the start of the forum page should be the first one you see,
it has more detailed instructions and will work with your manual.
 
A

auchandler1

Seaman Apprentice
Joined
May 27, 2011
Messages
41
Re: Force 125 shakes at low RPM

I read that a little bit ago. Now before adjust the screws should you screw them all the way down then adjust it or opposite?

The carb specs says that the factory setting should be 1 turn out from light seat.
 
B

bentle

Chief Petty Officer
Joined
Aug 2, 2011
Messages
492
Re: Force 125 shakes at low RPM

Yes clockwise until it stops very gently. The manual does it by the book or factory settings.
You may need to fine tune it depending on your altitude, but if that's to difficult then do by the book or the sticky.
 
A

auchandler1

Seaman Apprentice
Joined
May 27, 2011
Messages
41
Re: Force 125 shakes at low RPM

I will do this tomorrow when we bring the boat out. I'll let you know the results...
 
jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,969
Re: Force 125 shakes at low RPM

Idle mix screws???? There are air screws.They are on the side or front of the carb.
The idle screw is on the side of the motor.It's use is to raise or lower the RPMS.
The air screws are to adjust the amount of air/fuel at idle.
Best done in the water.
Do the linc and sinc in the first post.Then set the air screws.
If the air screws are set wrong,to lean= burnt piston.Too rich=carbon,smoke,eventual failure.
 
A

auchandler1

Seaman Apprentice
Joined
May 27, 2011
Messages
41
Re: Force 125 shakes at low RPM

Jerry please look at the picture above. Those inlet needles that are in what appears to be springs on each carb is this the so called air screws you are talking about. I have looked at a few manuals and parts diagrams and nothing said air screws, they just tell me mix screws or idle mix screws.

The idle screw you are referring to is the idle speed screw found on the bottom of the timing tower. It has a locknut on it..
 
jerryjerry05

jerryjerry05

Supreme Mariner
Joined
May 7, 2008
Messages
17,969
Re: Force 125 shakes at low RPM

Those are the ones you adjust for air/fuel.
.It might make a difference in the rpm's.
Just don't try to set the RPM's up with them.
Some people say to turn them in after you set them to optimize the mix.
Just follow the directions from Seloc or what I posted.
After you get them right.See how far in they go.It should be about 1 and 1/16 turn out.Somewhere around there.
Remember the setting.Then once in a while check the setting.They vibrate loose even with the spring.
 
B

bentle

Chief Petty Officer
Joined
Aug 2, 2011
Messages
492
Re: Force 125 shakes at low RPM

air fuel mix screw.jpg
This on my 89 125 force outboard, yours should be the same or similar.
Hope this helps.
 
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