1980 johnson 100 horse missing?

[Stick1377]

I have a 1980 Johnson 100 horse. Hard to start at times when cold. My biggist problem though is when it is finally warmed up and idling it has an unusual miss. It might run goog for a few minutes or none at all and then it just jerks hard and the motor almost dies. Sometime it does this two or three times in a row and others just once. Most of the time the engine will stumble but recover without dying but is very aggrivating. It has new plugs gapped correctly and carbs are clean and rebuilt. I installed a clear fuel filter in line due to the boat sitting for awhile and fuel looks very good. Any ideas would be appreciated.

 

[kybill66]

Re: 1980 johnson 100 horse missing?

while the motor is running get some insulated pliers and pull spark plug leads off one at a time. what i mean is pull one and then hold it close to the end of the plug to see if it hits. Then do it to the rest of them it might even die if is only running on the plug wire that you pulled off.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

Ok I'll try that. Maybe a day or so before i can respond. Thanks for the idea.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

I quess I should have mentioned earlier that it only does this at an idle. If going across the lake it runs great. Open for any more suggestions. Thanks

 

[emdsapmgr]

Re: 1980 johnson 100 horse missing?

You may have a carburetion issue called a "lean sneeze." It is not electrical, but a fuel issue. Did you do a sync and link when the carbs were reinstalled?
Possible one of the carb butterflys is ajar letting in extra air at idle causing a sporadic lean miss condition.

 

[scrampbell]

Re: 1980 johnson 100 horse missing?

Two thoughts...

1. When you cleaned and rebuilt the carbs did the tiny holes on the main jet look crisp and clear? Only thought of this because I also had symptoms of dying mainly at idle.

2. I'm going out on a limb here and saying that it's mainly your impeller that is magnifying other smaller issues that would normally be okay. When's the last time you changed the impeller? Where do you run this boat mainly?

 

[cdoliver]

Re: 1980 johnson 100 horse missing?

check your compression. check your spark, how old is the fuel? will it idle in neutral in the water? you may have to look at the carbs again.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

Forgive me, I've worked on cars all my life but just starting on boats. How would a sync and link be done? I understand what you are getting at but could use some instruction. The boat had ran fine with carbs as they were before it sit for years. I didn't change any of the linkage settings, just unsnapped them. How do I go about syncing them?

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

Yes the holes looked fine after using some carb cleaner and an air compressor. What impeller are you talking about? I really am just figuring boats out. The boat has mainly been used on wright patman lake near texarkana.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

Now i did notice the fuel pump diaphram is a little stiff, possible has a very fine crack in one side. That could cause the lean issue, but i don't understand why it gets better at full throttle going across the lake.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

Spark is steady and blue, fuel is less than two months old. I don't have a compression guage, last one got broken and never bought a new one. Just to listen to it turning over it doesn't sound like it has a weak cylinder....I guess they all could be weak.....As far as idling in the water it really doesn't change anything from using the hose attachment to being in the water.

 

[cdoliver]

Re: 1980 johnson 100 horse missing?

I'd do a compression test just for piece of mind. Did you remove All of the jets when you rebuilt the carbs. It really sounds like you have a partially clogged idle jet OR somewhere between the tank and the carbs there is an air leak. Can you pump the fuel bulb up where it gets hard and stays hard?

 

[mikesea]

Re: 1980 johnson 100 horse missing?

a manual is the way to go,but ,the sinc and link at the CARB is a matter of using the adjustment screw on the linkage ,you want both butterflies to open in unsion,also,the roller that allows for carb advancement may be worn,some older engines had a plastic piece that looked like clear hose over the roller,if your roller seems to have a depression about 3/8 of an inch,the plastic I mentioned may have dry rotted off,Ive substituted with a piece of fuel hose and made it.It is possible that as the other poste mentioned,your idle circut may have issues,the idle fuel passes through the brass passages and unless the dirty carb was soaked in a good cleaner and pressure blown ,there may still be dirt.I'm betting on the sinc and link and or your roller

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

I'll check the linkages to see if they are working together. The plastic peice you are referring to looks like it has been replaced at some time because it really has no wear on it. I'll try to find a manual. how do you feel about the fuel pump diaphram i mentioned earlier? I've had people say that could cause it at an idle. I'm really not sure how it works...vacuum? cylinder pressure?. I'm accustomed to manual or electric and it is neither. Thanks for your ideas.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

I'm going to buy a compression tester tomorrow to check the cylinders. If it could be taken out with a screwdriver i took it off. I soaked everything in berryman chem dip and finished off spraying with carb cleaner and blowing out with air compressor. There is new line from the tank to the motor, but i haven't seen the line going into the tank. I'll have to check that. The bulb will prime up hard but doesn't stay that way very long. That may very well be the problem. Is there any chance that adding the inline filter before the motor is making it too hard for the pump to pull the fuel? I really appreciate your (and everyone's) ideas.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

Ok I pulled up a schematic of the carb and yes I did pull the jets out. I am sure that those carbs are spotless........Unless there was some grit or something in the line from the pump to the carb. After cleaning/rebuilding them i took the pump apart and there was a good bit of grit that had settled in the bottom. I guess I should pull them back down to see? I even replaced the fuel lines that connect the carbs together due to the old ones being so dry rotted. Again thanks for any ideas.

 

[scrampbell]

Re: 1980 johnson 100 horse missing?

You get this fixed yet Stick?

With your stiff diaphram and possible small crack causing your lean issue I'm wondering if there is another catalyst that would cause it to have the weird miss you described. Since the water pump and other components run off of the motor if there were something that would cause occasional extra strain on the motor (broken tooth in the impeller assy, bad bearing somewhere or something else that briefly binds up) then that would magnify your lean issue causing the engine to die at times.

Because it jerks hard, I've got to think that something is temporarily binding up and it essentially chokes the motor out.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

Finally, I worked on that motor all day yesterday. rebuilt the pump and realized it wasn't put together right in the first place. checked everything i could think of and still no change. Well i should have checked to see if the carbs were as in sync as I thought. And they weren't, at idle the top butterfly was open about 1/8 inch while the bottom was closed completely. I guess I bumped it out of place when i was working on them. Adjusted them a few times and finally got the idle fixed. Went out on the lake and it runs great. My only problem now is it occasionally stays idled up for a breif period after pulling the throttle back. I think this will get better with use, I might rig up a throttle return spring if I can figure out how. Thanks to you and everyone for all the help.

 

[emdsapmgr]

Re: 1980 johnson 100 horse missing?

Could be just a minor adjustment of the throttle cable end in the cowling.

 

[Stick1377]

Re: 1980 johnson 100 horse missing?

I considered that and removed the throttle cable, started the motor and revved it up by hand. I could let go then and 9 times out of ten it didnt want to idle down all the way.