Force 120 1976 - Was running great, then gradually lost ability to idle. - Need Help Please

[MarcSinger]

So figured I’d give an update for anyone in the future, the fuel pump issue was due to a faulty rebuild kit, new kit and no problem with fuel coming out the 90 fitting any longer. After a compression test found 148-151-150-152. Actually surprised it was so high for a 97 motor. But came to the conclusion it was a carb issue. Rebuilt the carbs (again) changed fuel lines, filter (again) and found during carb rebuild it had .094 jets in it. Seemed a little big to me so I went to the Mercury parts website and saw that .088 jets were recommended for my altitude (800ft). Fabricated some jets from a couple of brass screws. Drilled a 5/64 hole (roughly .078) and cut them down to the size of a jet. Boom, she ran perfect, gets the boat up to 40mph running 5100rpm with 4 people and fully loaded with tools and fishing gear. Had some actual .088 jets ordered and put them in and it smoothed out the idle even more and gave a better throttle response. Set timing to 30 degrees ( going for 28 degrees after I do some linkage adjustments) and had it on the water for 4 hrs yesterday without issue. Almost certain the jets were the cause of the problem. Not sure why it had that big of jets in it, especially in NC altitude. Thank you all for your help!

Good Work getting your motor to run!!! I hope I can ask a few questions.

I am looking for suggestions, help, prayers, advice. I don't like giving up and want to understand how it works and what is wrong with it.

I have a Force 120 from 1976 (Yes 1976).

It was running awesome for a year, started to die at idle, and now I cant get it to idle at all.

I did the following:
1. Removed the carbs and rebuilt then with the exception of removing the Welch plugs on the tops of the carbs. (Didn't even know what they were for!?)
2. Replaced the fuel pump 3x. With a "compatible" Amazon version.
3. Installed Clear fuel lines to see if there was any air leaks. (There does seem to be air coming in at the inlet)
4. Checked for Spark on all plugs (Using a timing light on each lead going to the spark plugs. The timing light lit up so I assume the coils are working. I have not pulled the plugs and run them so I can visually see if there is spark.
5. Adjusted Timing using 28 degrees at WOT
6. Tore my hair out

Still wont Idle and I need help.
A. Your post helped me realize there should _NOT_ be fuel coming out the of the "Vacuum" right angle line and I had a ton of fuel in there. So I rebuilt the fuel pump (again 3rd time). I also used a vacuum pump to make sure it would hold vacuum. It seemed promising it was holding vacuum.
B. The fuel line going to the inlet of the fuel pump, after is primed with the bulb, would slowly have air coming into it. I can't figure out from where. So I tightened the 4 bolts on the fuel pump, and the clamp on the fuel line, and unfortunately broke the inlet nipple off the fuel pump. YAY !
C. So... I am waiting for a rebuild kit for my ORIGINAL fuel pump and am going to try again. (I dont think the Amazon pump is making good contact with the engine and gasket, thus the little hole between isn't making good pressure or vacuum to move the diaphragm) But who knows?
D. I also plan to remove the plugs at the top of the carb, and inspect for junk, clean them out, and Try again.


A few questions in general:
1. Where is the "Jet" located that you "fabricated yourself". Is it on the "Straw" that goes into the bowl of the carb, on the side of it. You can unscrew it with a Flat Head driver. I didn't measure the one I have in there, but what size should it be for my elevation?

2. I Live in St. Pete Florida Elevation is 0

3. How much pressure should the Fuel pump create. No matter what I do, with the fuel pump rebuilds it seems the pump is barely moving any fuel. When cranking the engine, before it fires up, should the fuel pump move a lot of fuel? (If I remove the outlet from the carbs.. just to see if fuel is coming out) It just seems to dribble out.

Thanks for anyone who can help!





I have a few questions about the fuel pump rebuild that you did an

 

[MarcSinger]

New to the Forums and I would love some help.

I am looking for suggestions, help, prayers, advice. I don't like giving up and want to understand how it works and what is wrong with it.

I have a Force 120 from 1976 (Yes 1976).

It was running awesome for a year, started to die at idle, and now I cant get it to idle at all.

I did the following:
1. Removed the carbs and rebuilt them with the exception of removing the Welch plugs on the tops of the carbs. (Didn't even know what they were for!?)
2. Replaced the fuel pump 3x. With a "compatible" Amazon version.
3. Installed Clear fuel lines to see if there was any air leaks. (There does seem to be air coming in at the inlet)
4. Checked for Spark on all plugs (Using a timing light on each lead going to the spark plugs. The timing light lit up so I assume the coils are working. I have not pulled the plugs and run them so I can visually see if there is spark.
5. Adjusted Timing using 28 degrees at WOT
6. Tore my hair out

Still wont Idle and I need help.
A. I saw a post that helped me realize there should _NOT_ be fuel coming out the of the "Vacuum" right angle line and I had a ton of fuel in there. So I rebuilt the fuel pump (again 3rd time). I also used a vacuum pump to make sure it would hold vacuum. It seemed promising it was holding vacuum.
B. The fuel line going to the inlet of the fuel pump, after is primed with the bulb, would slowly have air coming into it. I can't figure out from where. So I tightened the 4 bolts on the fuel pump, and the clamp on the fuel line, and unfortunately broke the inlet nipple off the fuel pump. YAY !
C. So... I am waiting for a rebuild kit for my ORIGINAL fuel pump and am going to try again. (I dont think the Amazon pump is making good contact with the engine and gasket, thus the little hole between isn't making good pressure or vacuum to move the diaphragm) But who knows?
D. I also plan to remove the plugs at the top of the carb, and inspect for junk, clean them out, and Try again.


A few questions in general:
1. How much pressure should the Fuel pump create. No matter what I do, with the fuel pump rebuilds it seems the pump is barely moving any fuel. When cranking the engine, before it fires up, should the fuel pump move a lot of fuel? (If I remove the outlet from the carbs.. just to see if fuel is coming out) It just seems to dribble out.

2. Once I rebuild the fuel pump, is there a good way to test it? I plan to check if it holds vacuum at the Vacuum "right angle" connector and the "Hole on the back" and from Inlet to Outlet with my finger covering the Outlet.



Thanks for anyone who can help!

 

[legalfee]

Had an similar issue with my 1995 90HP. Bad Regulator / Rectifier. Disconnect it if you go to WOT RPMs then it's the culprit.

 

[racerone]

The FORCE brand appeared in about 1983 / 84.-----Perhaps you have a Chrysler with a Force cowling..-----The fuel pump is driven by crankcase PRESSURE pulses.-----So look there for possible issues.-----Post your cylinder compression values.----That may offer some clues.

 

[MarcSinger]

The FORCE brand appeared in about 1983 / 84.-----Perhaps you have a Chrysler with a Force cowling..-----The fuel pump is driven by crankcase PRESSURE pulses.-----So look there for possible issues.-----Post your cylinder compression values.----That may offer some clues.

@racerone Thank you for your reply!

OK Cylinder compression Values:
#1 115 PSI (Top Cyclinder)
#2 130 PSI
#3 150 PSI
#4 140 PSI

Video of the Motor running, then stopping, unless I squeeze fuel bulb.

A. I rebuilt a replacement fuel pump, tested it with a vacuum pump for leaks, it seems solid. Used Permatex #1 as the Engine to the Port on the fuel pump to make sure I have a good seal.

B. I have replaced all fuel lines with clear fuel lines to see if there is any air in the lines. There is some air, but I cant seem to figure out where its coming from. (See the video link above)

C. If I squeeze bulb, engine keeps running. With some hiccupping.

D. There is some fuel coming out from the front air intake of the lower carb, but its a small amount. (See video link above). Is this small amount enough to think Reeds? I did inspect the reeds with a camera, and they visually looked ok. Should i them to inspect?

E. The body of the engine seems to be "Sweating" with a similar wetness mentioned in F below, which doesn't seem to be anything new. I am guessing it is the recirculation hoses, which I have not yet taking the time to replace.

F. One of the spark plugs seems to be "Wet" with a black lightly greasy feel to it. It doesn't smell like unburned fuel. I can post a picture of this if it is helpful.

Thanks again for any help you can provide. I hate giving up!

 

[racerone]

The compression values are an issue.-----Remove cylinder head and have a look.-----It could be a bad head gasket .----Or scored cylinders that will make you cry at an estimate to repair.

 

[jerryjerry05]

The motor in the video is from a 120 Force about 1995
The coils /pack are a Mercury added part, they took over about 94 and used their parts.
From the way the motor sounds it sounds like the carbs are set wrong, one running faster than the other. Loosen the tie bar and reset the butterflies to open at the same time.
Check/ rebuild the fuel pump?
Do this first, the primer: has a tiny hose that runs to the float bowl, pinch it off and see if it runs better, there's a rubber diaphragm in the primer that can go bad and allow excess fuel into the carb and flood the motor.

 

[jerryjerry05]

I answered this in the post you hacked.
Always start your own.
The motor in the video is from a 120 Force about 1995
The coils /pack are a Mercury added part, they took over about 94 and used their parts.
From the way the motor sounds it sounds like the carbs are set wrong, one running faster than the other. Loosen the tie bar and reset the butterflies to open at the same time.
Check/ rebuild the fuel pump?
Do this first, the primer: has a tiny hose that runs to the float bowl, pinch it off and see if it runs better, there's a rubber diaphragm in the primer that can go bad and allow excess fuel into the carb and flood the motor.

 

[MarcSinger]

The motor in the video is from a 120 Force about 1995
The coils /pack are a Mercury added part, they took over about 94 and used their parts.
From the way the motor sounds it sounds like the carbs are set wrong, one running faster than the other. Loosen the tie bar and reset the butterflies to open at the same time.
Check/ rebuild the fuel pump?
Do this first, the primer: has a tiny hose that runs to the float bowl, pinch it off and see if it runs better, there's a rubber diaphragm in the primer that can go bad and allow excess fuel into the carb and flood the motor.

Thanks for your reply. I think the primer is good. Its the only thing that allows the motor to start. If I crank the motor it wont start until i push the key in to open the primer then it starts right up and then dies after that prime fuel is used.

 

[MarcSinger]

The compression values are an issue.-----Remove cylinder head and have a look.-----It could be a bad head gasket .----Or scored cylinders that will make you cry at an estimate to repair.

OK Will do thanks for the input I will report back.

 

[jerryjerry05]

Before you remove the head: get a snake camera for your phone and have a look at the cylinders or a long skinny screwdriver and turn the motor so the sd goes all the way in and see if you can feel any cuts or grooves in the walls.
The spark plugs all burning the same or is #1 clean? Pics?

How you doing the compression test?
If the motor keeps running only if you keep engaging the primer then There might be a fuel delivery problem. The connectors on fuel line can go bad and the squeezie can go bad too and allow the fuel to backfeed to the tank. I found over time that removing the connectors and running straight fuel line solves some problems(I've owned 8 different Forces, 85/90/120/125)
The squeezie is supposed to block fuel from going the wrong way.
If the connectors bad it can suck air and stall?
Testing the primer: motor running: unhook the hose at the primer and pinch it off, then activate the key and see if the primer shoots fuel? The motor needs to be turning for the primer to get fuel pressure.

If you can keep it running: do the starting fluid test. Running, spray sf around the intake side of the motor, under/around the carb bases and under the ignition system(coils/pack). Any changes in the way it runs can indicate an air leak or sucking air.
The 4 port covers have gaskets that can blow with one tiny backfire or even a cough/backfire. That can cause the piston to run hot?

 

[oldboat1]

Might spray around the base of the powerhead as well. A change in rpm indicates a leak.

 

[MarcSinger]

Before you remove the head: get a snake camera for your phone and have a look at the cylinders or a long skinny screwdriver and turn the motor so the sd goes all the way in and see if you can feel any cuts or grooves in the walls.
The spark plugs all burning the same or is #1 clean? Pics?

How you doing the compression test?
If the motor keeps running only if you keep engaging the primer then There might be a fuel delivery problem. The connectors on fuel line can go bad and the squeezie can go bad too and allow the fuel to backfeed to the tank. I found over time that removing the connectors and running straight fuel line solves some problems(I've owned 8 different Forces, 85/90/120/125)
The squeezie is supposed to block fuel from going the wrong way.
If the connectors bad it can suck air and stall?
Testing the primer: motor running: unhook the hose at the primer and pinch it off, then activate the key and see if the primer shoots fuel? The motor needs to be turning for the primer to get fuel pressure.

If you can keep it running: do the starting fluid test. Running, spray sf around the intake side of the motor, under/around the carb bases and under the ignition system(coils/pack). Any changes in the way it runs can indicate an air leak or sucking air.
The 4 port covers have gaskets that can blow with one tiny backfire or even a cough/backfire. That can cause the piston to run hot?

1. Did Compression test with all spark plugs removed. Ignition off. Engaged starter by energizing the solenoid.
2. I inspected with camera. Some scoring on cylinder #2 but that cylinder doesn't have the worst compression

#1 115 PSI (Top Cyclinder)
#2 130 PSI
#3 150 PSI
#4 140 PSI

3. Will the starter fluid test be valid considering the engine keeps running if I squeeze the bulb?

4. Any recommendations on testing the fuel pump pressure? Is there a spec for the pressure it should create on the output?

5. Only markings I can find on the motor seem to be serial number Labels and they are illegible. Can I look somewhere on the engine block for a stamp with a part number so I can nail down the year of the motor to get a proper service manual?

 

[racerone]

I think motor needs to come apart for proper repairs !

 

[WIMUSKY]

Those compression numbers are all over the board. They should be equal, or no more than 5% difference.... Maybe squirt some oil in each cylinder, spin it over a bit and retest. I personally like to test with a warm motor... But since you have scoring, ummmm.......

 

[jerryjerry05]

On the block under the coils/packs is a foundry stamp.
The numbers in the middle of the circle is the year.
Also under the bottom carb on the intake is another foundry stamp.
Sometimes the starter will have a year on it(if it's original).

The comp #s : that motor was designed to have a difference of about 10# between the top, bottom and the 2 middle cylinders.
150 #1/4 and 140 #for #2/3 so #1/2 could have a bad gasket between the first 2 cylinders.