120 Force Outboard carburetor question(s)

[kiker14]

Hi All,

I'm very new to boating although I have moderate mechanical experience from working on (newer model) cars. That being said, I've never had a car with a carburetor so even though it's old technology, it's new to me.

I have recently purchased a 1992 bayliner capri with the original force 120 outboard. The boat is in great shape, but the engine needs some TLC. It was running moderately well a few weeks ago, but when I took it out this past weekend, I ran into issues. Basically, after the engine was running while in neutral lock, and giving as much throttle as possible while in neutral lock, as I brought the throttle back to put it into the neutral position so I could then put it into gear, it would stall.

Thinking I was adjusting the idle, I messed with the wrong screw (the timing screw under the flywheel). I did not move it too far, and when I realized it wasn't helping, I moved it back. Just in case I'm going to get my hands on a timing light to make sure I am in the 28 deg range.

While fiddling around, I also messed with the screws that are on the top of the carburetors, the ones that are about 2 inches back, and that have the springs. I was a little frustrated at this point so I wasn't paying enough attention to where they started out. Right now they are about 2 full rotations out from being "seated" although the spring did not fully compress when "seated" - I didn't want to force anything.

While the engine was warm I was still able to start it every time, but it would stall every time when going into neutral. Now, a few days later, I cannot start it at all. I am using earmuffs in the driveway.

After reviewing the owners manual for the motor, it doesn't mention the screws with the springs on them at all, it only talks about a "needle valve" and the picture indicates that it's adjusted by the little white plastic screw that can be accessed by putting a screwdriver through the hole in the air plate. I actually haven't been back out to the boat since looking at the manual, but I do remember that the white screws on each of the carbs that are accessed through the air plate were screwed all the way in. Are these the screws that are supposed to be 1 turn out initially, and then adjusted? Have I been way too lean? What's the difference between functionality of these white plastic screws on the "front" of the carburetor (facing the boat) vs. the screws on the top of the carburetor that have the springs around them (facing the starboard side)?

Sorry if this is a dumb question, I'm just trying to get this thing running properly and after searching I didn't find any exact answer to these questions. FYI I have also now adjusted the actual engine idle screw but as I mentioned, I have been unsuccessful in even starting the engine so I'm not sure if that has resolved my stalling issue when going into neutral from neutral lock/high idle.

Thanks!

 

[Frank Acampora]

Re: 120 Force Outboard carburetor question(s)

The carbs on various model Force engines do have different low speed needles. What remains constant is that all are initially adjusted to 1 1/4 -1 1/2 turns out from lightly seated. At this setting if nothing else is wrong, the engine will start and run.

These engines and ignition systems use a surface gap spark plug. The plugs do tend to foul easily. The first indication is stalling when put in gear, stalling at idle, hard starting, or failure to start.

Because the ignition systems deliver the weakest spark at idle, IF you can get the engine started, it will usually run well at higher speeds--again, if you can get it in gear without stalling.

SO: First set the low speed needles, then put in a new set of plugs OR clean the old ones well with a Skotchbrite pad and try to start it..

Then read the sticky in FAQs: Synchronizing carbs and timing.

 

[kiker14]

Re: 120 Force Outboard carburetor question(s)

The carbs on various model Force engines do have different low speed needles. What remains constant is that all are initially adjusted to 1 1/4 -1 1/2 turns out from lightly seated. At this setting if nothing else is wrong, the engine will start and run.

These engines and ignition systems use a surface gap spark plug. The plugs do tend to foul easily. The first indication is stalling when put in gear, stalling at idle, hard starting, or failure to start.

Because the ignition systems deliver the weakest spark at idle, IF you can get the engine started, it will usually run well at higher speeds--again, if you can get it in gear without stalling.

SO: First set the low speed needles, then put in a new set of plugs OR clean the old ones well with a Skotchbrite pad and try to start it..

Then read the sticky in FAQs: Synchronizing carbs and timing.

Thanks Frank! I did actually read the sticky and watched the youtube video - very, very helpful! thank you for taking the time to put that together! I hope to get my hand on a timing light this evening to set the timing. The carbs appeared to be synced up already, the butterfly valves opened and closed with one another very well and seemed equally responsive to the throttle position.

Do you know why there might be 2 separate screws on each carb and what their functions are? I'll try to move the plastic screws out 1.25-1.5 turns and then see if it will start up (since the other screws with the springs attached to them are already turned out that much).

The spark plugs are brand new, but I can still double check them to see if they have fouled up in the ~20 minutes they have been used.

The previous owner also had idling issues, he would just snap it into gear real quickly to keep it running, but for a novice boater, I don't feel comfortable doing that and feel it might make my docking and un-docking in a no wake zone very difficult or possibly dangerous.

 

[pnwboat]

Re: 120 Force Outboard carburetor question(s)

If the plastic screws are what I'm thinking they are, those are actually screw in plugs that seal off the idle air jet passages. They should not be loosened up at all. If you remove them and look closely into the passage, you'll see a small brass slotted jet inside. The idle speed is adjusted by the screw with a lock nut in the picture below (red arrow).



Idle speed in the driveway with water muffs should be 900 - 1000 RPM in neutral, about 750 in the water in gear.

 

[kiker14]

Re: 120 Force Outboard carburetor question(s)

If the plastic screws are what I'm thinking they are, those are actually screw in plugs that seal off the idle air jet passages. They should not be loosened up at all. If you remove them and look closely into the passage, you'll see a small brass slotted jet inside. The idle speed is adjusted by the screw with a lock nut in the picture below (red arrow).

View attachment 196214

Idle speed in the driveway with water muffs should be 900 - 1000 RPM in neutral, about 750 in the water in gear.

Thanks pnwboat.

I will take a look in the passage - I just found it interesting that in the owners manual, they have an image of a screwdriver tuning those screws on the "front" of the carbs, not the screws on top.

I did manage to modify the idle screw (and i also moved the timing screw which was in your image with the yellow arrow - but I've moved it back and will get a timing light to confirm that my timing is set properly).

Thanks!

 

[jerryjerry05]

Re: 120 Force Outboard carburetor question(s)

Hard starting and poor idling.
Do a compression/spark test. Just to make sure there is nothing wrong with the motor.
The air screw is the only thing you turn on the carb.
It's the one with the spring.
The pic you seen is from an old carb. They had the air screw on the front/top.
What owners manual are you using? The factory is the best. The Clymer and Seloc is a poor second choice.
The idle should be about 750-800 in gear. In the driveway about 1100???

 

[kiker14]

Re: 120 Force Outboard carburetor question(s)

Just to show I'm not crazy, here is a screen shot of a similar image to the one found in my owners manual:



Instructions are:

1) Start engine until fully warmed up
2) Return control level to "neutral" position
3) adjust one carburetor at a time. Turn idle adjustment needele on top of carburetor slowly counterclockwise (open) until engine loses power and begins to roll or gallop due to an over-rich mixture. Slowly turn needle clockwise (close) until engine runs smoothly and begins to pick up speed. Continue turning clockwise until engine pops or stalls due to a lean mixture. Set adjustment halfway between these two points
4) Adjust both carburetors in the same manner. Do not adjust leaner than necessary to obtain smooth idling. It is better to have the idle setting a little rich rather than too lean

Is this what you guys adjust, or are you just adjusting the screws on the top of the carb that are held in by the spring?

Just so we are talking about the same thing, the screw on the top I have circled in pink (there is one on each carb but the bottom one you can't see in this picture because it's behind the cam)



Thanks!

 

[kiker14]

Re: 120 Force Outboard carburetor question(s)

Hard starting and poor idling.
Do a compression/spark test. Just to make sure there is nothing wrong with the motor.
The air screw is the only thing you turn on the carb.
It's the one with the spring.
The pic you seen is from an old carb. They had the air screw on the front/top.
What owners manual are you using? The factory is the best. The Clymer and Seloc is a poor second choice.
The idle should be about 750-800 in gear. In the driveway about 1100???

thanks Jerry. I will be picking up a compression tester tonight to make sure nothing is wrong. The previous owner took me out on it a few weeks ago and it was fast enough to blow hats off of our heads, so I believe the motor is in good shape overall.

The owners manual is the one provided by force, I believe it is the original manual that came with the motor. When I get home I can take a picture of it. I just posted an image that is from a similar owners manual but for a slightly different/newer motor.

I also have purchased a non-touch tachometer so I'll be testing the RPM's if/when I get it running.

 

[pnwboat]

Re: 120 Force Outboard carburetor question(s)

Yes screw with spring circled in pink is the idle mixture adjustment. 1 1/4 to 1 1/2 out from lightly seated will get you close to where you need to be. Image of the carburetor in post #7 is like Jerry said, an older carburetor.

 

[jerryjerry05]

Re: 120 Force Outboard carburetor question(s)

The pic you see is from the older carb. It's air screw was on the right like in the pic.
The new carbs it's on the left.
The white thingy is called a metering cup it may have a jet under it?? Don't touch.
The initial setting is 1 turn out. Then start and warm, turn slowly in till it bucks and then out 1/2 turn.
That will put you in an area that should be good.
In too far and your too lean, out and too rich.

 

[kiker14]

Re: 120 Force Outboard carburetor question(s)

Hi All,

I hate when issues are resolved but the original poster doesn't come back to tell everybody and we are all left wondering...

cliff notes: I was able to get the motor running again!

Longer version:

One thing I didn't mention is that yesterday I sprayed some carb cleaner on the inside and outside of the carb. Today, it was MUCH easier to screw in / out the adjustment screws, I think they were way too far out before (it was 4-5 turns in before they were lightly seated). I adjusted them properly, and also leveled out my boat so that I could put the motor all the way down. It was slightly tilted up so I think that may have been working against me as well.

I purchased both a compression tester and a timing light. compression was as follows:

Cyl1 = 115
Cyl2 = 60
Cyl3 = 130
Cyl4 = 125

It seems as if there may be some issues there, I'll check the compression again tomorrow now that the motor ran for a little while.

Using a timing light, the timing was way off, it was at about 15 degrees. I've moved the screw basically as far as it can go, and I'm still only at 24-25 when at "fast idle" I didn't jumper to try WOT. Once I've extended that screw as far as it will go before it falls out of the plastic housing, and need to go farther, what do I do? I haven't done a search yet for that so I apologize if that's been covered here before.

After it was warmed up, I used a touchless tachometer and it indicated 700RPM idle speed, so I think I need to adjust the idle screw on the throttle a bit more, but as you recall from my first post, in the past I couldn't get it to idle at all so I'm definitely moving in the right direction.

I still want to get the timing right, and spray some carb cleaner into the carbs while the motor is running to make sure it gets in there all the way, and I also want to run a tank of concentrated seafoam (along with a proper oil/fuel mixture). I'll report back once I've done some more tweaking, but I think I'm in good enough shape to get her back out on the water this weekend!

Thanks for the help so far! I'll try to make a video to help out others going forward...

 

[jerryjerry05]

Re: 120 Force Outboard carburetor question(s)

The timing, did you advance the throttle when you tried the timing?
The plugs all out? The plug leads all grounded?
Timing doesn't usually jump unless someone's messed with ??
Seafoam is a waste of $$$ Mercury's, Power Tune or OMC's Engine Tuner. Both are the same product.
Both work 100% better than SF.
The 700 will go up when the comp goes up.

The comp that bad on the top two cyl. Could be a head gasket??
If not then usually a 60# reading means a rebuild.

Pull the head and check for damage.
Profile,Location? You might be close to someone who can help?