1989 Johnson 20 hp not idling

[psteurer]

I just bought this motor. It starts easily but then sputters and dies when idling. It does run well at high speed in a 50 gallon drum. I do not have a tach but if I keep the fast idle lever on the remote up just a bit it will maintain the idle although it occasionally sputters. Compression is 115 and 118 psi on the two cylinders. The motor has a primer solenoid and it is in the correct run position.

As a solution, I decided to rebuild the carburetor. I noticed the carburetor was very clean as I completely disassembled it. Idle mixture needle and seat looked perfect as well as the float inlet needle and seat. It has a high speed and intermediate speed an orifice and these looked goo. I did notice two things:
1) with the carb upside, the float was not parallel but set so that the end without the hinge was about 1/8 inch LOWER than the hinged end of the float. I understand the float should be parallel and some posts I have read say to set the float so that the end without the hinge is just a touch higher. How should I set the float and would the 1/8 inch LOWER setting cause an idle problem?
2) the brass high speed nozzle was not in the center of the surrounding brass emulsion tube but actually touching the brass emulsion tube. These are the tubes that go from the carb bowl through the float and up into the venturi. It does not look like the small holes in the emulsion tube are blocked in anyway. Would this cause an idle problem and what can a I do to fix this if it is a problem?

It is a lot of work to reinstalled the carburetor and then reconnect the starter bracket so I thought I would ask about these two things before I gave it a test. It is also winter and not that much fun running a motor in a barrel.

 

[tashasdaddy]

Re: 1989 Johnson 20 hp not idling

i just did the same motor. the tube belongs out of center, the fixed jets need to be removed and clean. follow the below directions, i set my float just a smig, high, the other way may flood the carb. use a carb rebuild kit, don't try to use used parts. to adjust float, i hold the hinged end with needle nose pliers, and with a little pressure adjust the other side.
http://forums.iboats.com/showthread.php?t=244013
also, you may need to do a link n sinc, this sets the timing and carb so they work together.

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

Thanks. I am glad those brass tubes belong out of center. I have the carb kit and will put the parts in tonight and set the float like you say. I did remove the orfices and cleaned them. The link and sync might be beyond my ability. I have the 1989 OMC manual and I have read the steps for this. I don't have some of the special tools needed like I think something called a cam accentuator. I also don't have a timing light but I see they have some that are fairly inexpensive. I suppose I can give this a try if the carb rebuild does not work. Are there any steps for a link and sync on this forum?

P.S. I forgot to mention that when I bought the motor, the previous owner had the electric primer solenoid set on manual position. The motor would not die at idle when it was in this position but it smoked and there was a lot of unburned gray oil in the water barrel after I ran it. When I switched the red lever to the correct run position the smoking stopped but then it would sputter and die at idle. The thin primer hose that went to the upper part of the carburetor was slightly blocked. The lower hose that went in to the manifold was okay. So it might be the previous owner compensated for the bad idle by having the primer always in manual mode. I guess with one primer hose blocked the motor would not flood.

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

Thanks for the link and sync advice. Last night I installed the rebuilt carburetor and started the link and sync process as outlined in my OEM manual. I found with the motor in neutral that the cam follower was way off; about an inch to the left of the two marks. But I could push the cam with my fingers and the follower would then be between the two marks. So I looked at the throttle control rod and I found a problem that hopefully what was causing my bad idle.

There are two 3 inch silver brackets that hold the throttle control rod assembly on the top and the bottom of the motor. The bottom bracket was as loose as could be without falling out causing a lot of play in the throttle cable. I tightened the two bolts and made some adjustments to the cable trunnion screw. Now the throttle control touches the idle speed stop screw in neutral whereas before it was about 1/2 inch away. And the cam follower is between the two marks at idle (carb throat plate close).

So I think what was happening to cause my bad idle was the timing was way out of sync at idle but okay at higher speeds. With the fast idle lever on the control box up, everything was fine because the timing was synced to my carburetor. But when I started to lowered the fast idle lever, the timing did not retard as the carburetor plate in the venturi closed.

I will run the motor in the barrel this weekend to see if I got this fixed. I live in NC and temperatures are dropping in the 20s every night. So I might be breaking the ice in my test barrel.

 

[tashasdaddy]

Re: 1989 Johnson 20 hp not idling

one thing do not run it above, 1500 rpms, faster can cause the motor to run away, the only way to kill it is the move the primer knob to manual and flood it.

it sure sounds like you are on the right track.

also adjusting you cables could effect the idle speed.

on the port side, under the flywheel, is a white, plastic screw, at the linkage, this is your idle speed stop screw, it may need adjusting, to keep the linkage from coming too far back and killing the motor.

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

The motor will still not idle after the carb rebuild and link / sync. When cold, the motor starts after 2 or 3 tries with the fast idle lever up. It will stall a few times when cold but I can easily restart it with fast idle lever up. When the motor warms up, I can lower the fast idle lever about 2/3's down, anymore the motor will die. If I raise the fast idle lever back up I can keep it from dying. If the motor stalls, I can easily restart it with the fast idle lever up. I would say it is dying between 1000-1500 rpms (no tach). Any additional help would be appreciated.

This is what I have done so far:
-new spark plugs
-carb rebuild (but did not remove welch plugs); idle needle set at 1 3/4 turns
-link and sync (but did not do timing; do not have a light)
-compression test about 115 psi on both cylinders
-new spark plugs
-checked the primer solenoid for proper operation
-fresh fuel mix with 2 oz of Seafoam per gallon
-disassembled the fuel pump; cleaned filter; diaphragm looked fine
-spark test with two inline testers; consistent spark alternating between testers when I cranked the motor
-resistance test on both coils .05 ohms between ground and coil lead; 240 ohms between two coil leads.

I have an OEM manual. But one of the first tests I did before I even rebuilt the carbs was something I saw in the Clymer manual. It said to disconnect the fuel line from the carb and then pump the bulb to see if fuel went thru the fuel pump and then out the line before the carb which it easily did. The next test was to crank the engine 10-12 times and see if there is a constant flow from the fuel pump. No fuel came out of the line between the carb and fuel pump when I did this. So I took the fuel pump apart. The diaphragm looked fine but I am not sure what else to look for in there since the OEM manual does not have any schematic of the inside parts. At the time, I thought the fuel pump was okay since the diaphragm was fine. I also disconnected the fuel line from the T-fitting where it entered the primer solenoid and not at the carburetor (could not easily get at that fitting). I understand this type of fuel pump rarely has problems but now I am beginning to wonder. So here are some questions for my next tests:

1) is there a schematic for the inside of a fuel pump that would show the parts? my OEM manual does not show the inside
2) any other tests for a fuel pump I can do; I see a fuel pump gage in my OEM manual but I do not have one; I do have a MityVac but I think that gage only measures vacuum and not pressure
3) should I remove those welch plugs in the carb; the carb was very clean when I rebuilt it. I think I could remove the welch plugs without removing the carb from the motor. It is a bear to remove the carb since I also have to remove the electric starter.
4) any other electrical tests I can do? All I have is a VOM meter. I am still wondering if I have some electrical problem.
5) anything else I can do

Thanks for all the help.

 

[tashasdaddy]

Re: 1989 Johnson 20 hp not idling

they top welch plug is above the low speed inlets to the barrel of the carb, it they are clogged, it would not get fuel. looking in the barrel of the carb, from the motor side, in the top are 2-3 tiny hole that allow the fuel to enter the barrel. i have been successful, using a paper clip to clear these, but what ever you push out, could very possibly re clog the later.

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

Thanks so much for the speedy reply.

If I removed that top welch plug, could I clean out those inlets? That seems like the better way to go. I have removed welch plugs before on a lawn motor carb. They were pretty easy to remove and then replace with the one that came in the rebuild kit. Is there some difficulty in doing this and can I do this without removing the carb from the motor? It is a bear to take that starter off, but I know how to do it now so I am sure it would go quicker this time.

I was starting to think this was a fuel pump problem. But you are sending me back to the carburetor where I thought the problem was all along. I do not recall seeing these smaller inlets when I had the carb off. There was a large inlet around this area where carb cleaner came out squirting out. I must have missed the small ones.

Thanks again for all your help.

 

[tashasdaddy]

Re: 1989 Johnson 20 hp not idling

they are extremely hard to see. yes you can, pull the core plug, and access them, i agree much easier, than pulling the starter and all. i use a sharp ice pick, pearce the plug, and pry it out. then i use a 1/4 inch extention or a 1/4 inch wood dowel, and tack hammer to insert the new core plug. with the carb still mounted, i would open the butterfly, and shine a flashlight into the barrel, to make sure you have them clean. they are directly under the core plug.

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

I removed the core plug to the carburetor last night. That revealed a hole about 3/4 inch deep by 1/2 inch wide and two small low speed inlet holes at the bottom that went into the carb throat. Sure enough the inlet hole closest to the motor was clogged. The other hole which was slightly larger was open. That small hole that was clogged was right over the throttle plate in the carb during idle. So if it was clogged I suppose no fuel would get into the carb at idle which would cause the motor to die. When you open the throttle a little, the other hole that was clear would start providing fuel and that would keep the motor from dying but it would run rough and sneeze. And if you really opened the throttle, then the intermediate speed circuit would take over. This would all explain why my motor would die at idle, run rough at 1000rpm and run great at higher rpms. As I wrote in a previous post, when I bought the motor, the electric primer solenoid was in the manual position. This allowed fuel to bypass the carb but the motor smoked like crazy and there was unburned gray crude that dripped out of the vent holes in the lower unit.

I did not have time to do a test run in a barrel last night to see if the motor now idles. I am sure itching to do this and maybe can do a test run before it gets dark tonight. Hard to believe that a little speck of crude about the size of the end of a paper clip would cause this. I am not convinced I have everything right yet but this is a step in the right direction to get me going. I bought this motor with a 1963 Sea King runabout boat that needs restoring. I need to get this motor going so I can start on that project.

Thanks for all the help so far

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

Well, I got a chance to run the motor last night in a barrel. It started up immediately and I got excited. With the fast idle lever all the way up, it started right up and idled smooth. But then as the motor warmed up and I lowered the fast idle lever, it started to die as before. I could keep it going if I pressed the key in to activate the primer solenoid. But if I kept doing this, the motor would smoke and cough. I could also keep it running by raising the fast idle lever as before.

I did a few other tests. I connected two inline spark testers to the spark plugs while it was running. The spark appeared consistent and strong between the two cylinders. These were $2.99 spark testers from HarborFreight. I pumped the primer bulb to see if that would keep the motor from dying. The bulb was hard and had no effect.

Is there a recommendation as to my next steps? I am thinking of removing the carburetor again and recleaning. I did not remove the core plugs and lead shots during my first carb rebuild. After removing the top core plug as suggested by Tashasdaddy, I found some crude in one of the inlet holes. I recall a core plug in the float chamber that maybe I should remove to see what is behind it. Also, what about all the lead shots on the external carburetor? Which of those should I remove? There was one lead shot that was right above the brass tubes that come up from the float chamber that I could not access during the cleaning. Is there a trick in getting these lead shots removed? I suppose I could use fishing split shots as replacements. I have some old ones that are lead. Should I test the fuel pump or is the fact that the motor runs good at a high idle mean the fuel pump is working okay?

Again thanks for all the help. I think this motor is going to run well once the idle problem is resolved.

 

[G DANE]

Re: 1989 Johnson 20 hp not idling

There is a keyhole-shaped siliconegasket around the low-speed needle. If it isnt soft and tight in the casting, replace it. The manual advises to use nail-laquer around the welsh plug to seal any false air leak. You can try that. Any false air it draws in, will affect the iddle. Also check that the recirculation hose on the intake is tight. Adjust the mixture, as manual advises, and do a sync and linck. Both has been discribed here, do a search on words

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

Thanks for the advice. In the process or recleaning the carburetor a few days ago, I took a very close look at all the idle components and all the advice given. I found two things:

1) there are two 1/4 inch passages that come up from the float bowl and out each side of the carburetor. I believe these are vents should the fuel inside the carburetor get hot. On the external carburetor, both of these holes have screens. On the carburetor diagram from my rebuild kit, there was a core plug on one of these external holes. It looks like these screens were always there, but next time I run the motor, I am going to put my finger on one of those screened holes and see if that improves the idle.
2) And now the real problem. I looked at the adjustable idle mixture screw (one with the spring on it) very carefully. It is made of steel not brass and the tip looked great the many times I looked at. This time I noticed a worn groove about 3/8 inch up from the tip. I manually inserted it in the carburetor and sure enough the groove is where it seated in the carburetor. I am betting that will be my idle problem. I have a new needle valve on order and I also ordered a new brass adapter where the needle valve screws in.

Parts should be here next week and I will give it a try. I know any damage on idle needle valve can make a good motor idle very badly. But I never thought to look that far up from the tip. I am also wondering how the groove got there in the first place since this is a steel needle valve. The groove is worn smooth almost like it was made that way.

 

[psteurer]

Re: 1989 Johnson 20 hp not idling

Success! I installed the new idle needle valve and backed it out 1 3/4 turns per the manual. I pumped the bulb and raised the fast idle lever on the remote. It started on the first crank. As I lowered the fast idle lever, the motor held the idle at a very low rpm (no tach). It also restarted very easily with the fast idle lever down. The idle was fairly smooth but not perfect so I tried turning in the needle valve 1/4 turn per the posts I have read here. I probably turned it in 3/4 of a turn in total and did not really notice any difference in the idle. I will probably do a lake test soon and put her in gear to blow out some carbon. I am sure it is loaded and I will use the decarb procedure I read here using Seafoam. Then I will adjust the idle.

I would suspect my problems were a clogged inlet in the idle circuit and the grooved needle valve. Thanks for all the help in this forum. The advice given kept me on track with the carburetor and not wasting time and money on the fuel pump or electrical system.

P.S. The new idle needle valve part I bought would not screw very far into the old brass adapter. Luckily I had also bought a new brass adapter. These were new OEM parts. Both the old needle valve and new needle valve screwed into the new brass adapter. I suspect there was some minor difference in threads with the old brass adapter.

 

[samo_ott]

Re: 1989 Johnson 20 hp not idling

I've been following your thread as I have a '81 J35hp with similar issues but will not be able to run it again until the spring. That's good you got her runnung.