Here we go again Johnson 20 hp

[jamesh76]

I have posted a few times earlier about this motor. It is a 20r72r 1972 20 hp johnson.

As in recent posts I stated that a mechanice replaced the points, condensers, plug wires, rebuilt the fuel pump and checked + cleaned the carbs.

Here is the series as it goes now.

1st time out would idle great, but would not plane out. It felt as if I was riding a wheelie across the lake.
Repair------Bad fouled spark plug.

2nd time out motor would miss and acted like it was not running on both cylinders.
Repair----The insulation on my wire from my electric start button was bad and supposedly was arching to the engine fouling the bottom plug again.


3rd time started in a barrel just to see how it ran. Heard a loud clanking noise.
Repair-----Mechanic did not get the nut on the fly wheel tightened all the way

4th time out Motor ran great and would start fine. When i went to give it full thottle it would rev up and down as if it was not getting gas or something.
Repair---- The spark plug wire was bad and fouled the bottom plug for the third time. Plug wire was replaced, It had a cut in the insulation.

5th time (today) went out and tried it in a barrel. I noticed gas dripping from the fuel pump that was rebuilt on the first go around. I bought a new fuel pump and put it on. Now the motor starts ok, it idles good most of the time but sometimes it is rough and has a coughing sound. I have pumped the bulb and it is still tight and makes no different result. When it coughs it will act like it is revving up and down you kinda here a klunk when it does this. Sometimes it dies sometimes it does not.

Is there any suggestions to a fix on this or what may be wrong. I feel as if i have had too many misfortunes from the prior (fixes) to take it back to the mechanic.

 

[jamesh76]

Re: Here we go again Johnson 20 hp

Also the fuel is mixed 50:1 and i have also tried adjusting the lean/rich mixture with no better results.

 

[HybridMX6]

Re: Here we go again Johnson 20 hp

Is there an idle speed adjustment on that motor? I had a 1970 20hp and it had one in front of the carbs. It sounds like it's lean sneezing: coughing as it runs out of gas at idle, then recovering, then repeating. Just a suggestion to try until others pop in also.

I definitely would NOT go back to that mechanic. He obviously didn't check his own work, and I would not trust him at this point. If it can't be figured out from help on the forum, worst case is try to find a different mechanic. I'm pretty sure it can be fixed though the forum though, as it seems mostly anything can as long as the person doing the work can handle it.

 

[jamesh76]

Re: Here we go again Johnson 20 hp

Thanks. I will look and see if I can locate it. I have not recieved my manual yet for this motor So any advice of location and or what I am looking for there would be appreciated.

 

[HybridMX6]

Re: Here we go again Johnson 20 hp

Well, mine had a needle or something I guess, coming out of the carb. Take off the hood, and on mine there was a black cover over the front of the carb. The knob was sticking out of there and said "Idle adjustment" on it I believe. I was always told screw it all the way in (gently), then back it out a turn and a half (1.5), and go from there. Adjust it to where it idles without coughing, but doesn't idle so high you feel it isn't right. It's been about 9 years since I had that motor, and man do I miss it. It was one of the best running motors I ever had. The water pick up sucked being behind the prop, but other than that, it ALWAYS started 2nd pull, ran great. Just got a larger boat and it wasn't big enough any more.
Hope some of that helped ya (not my rant about what a good motor, but the idle speed knob).

 

[jamesh76]

Re: Here we go again Johnson 20 hp

Ok, I looked at mine. On the front of the carbs infront of the air filter there is a bolt that comes out with a plastic piece. This piece has a little "L" spaped bar or wire that connects to the lean/rich nob. Is this what you are talking about?

At first I only moved it the amount that i could with the lean rich adjustment and it was kinda hard to turn. Then i took the wire off and started playing with it and turning it. I turned it out 1 turn and started fine adjusting it. I could get it where it would idle pretty smooth and then I would turn it where it would cough and make that klunk sound. I pulled the little plastic piece off and set it so that it was right in the middle of my adjustment range. I am hoping this was the problem. It seems to turn a little bit easier than before. I am thinking that my mechanic had it possibly too tight where it was not backed out properly and not that I adjusted it I seem to have a better running motor. Since I have been typing this. I heard the motor rev up a little bit then settled down. Over all i have not heard the klumk or cough noise.

But if i move this adjustment much from where it is, say 1/4 a turn I hear the noise again.

Does it seem as if we may have located the problem?

Thanks, any more advice or a reply is appreciated.

 

[Rick.]

Re: Here we go again Johnson 20 hp

Sure sounds like a slow speed idle adjustment. Turn it out about 1/8 turn(counter clockwise) at a time until it stays smooth. I'm almost certain that's your fix. If it isn't, your discription could be caused by a leak of air into the gas line as well but try the slow speed first. Sounds like you've had your hands full with that motor. Best of luck. Rick.

 

[jamesh76]

Re: Here we go again Johnson 20 hp

All seems to be fine now. I have the slow speed idle? If that is the correct term. Well I have the lean/rich bolt that goes into the carbs backed out 1 3/4 turns. It seems to idle well there. I rev it up and it seems to slow down nicely. I put it in gear and it idles smoothly without dying. I then tested it at a higher rpm and cleaned most the water out of my barrel and shut it down. I refilled and then ran it at a mid range rpm where water wasn't coming out of the barrel. It ran fine and a occasionally when i let off the handle it would idle down and die.

If there are any other suggestions, Please bring them forward.

As always thanks to the great people of this site that help one another out. Some day I will have learned enough to contribute advice in helping others also.

 

[wbeaton]

Re: Here we go again Johnson 20 hp

It sounds like you may have found the problem. It was running lean and that's what caused the knocks and sneezing. Intial starting point is usually 1.5 turns out on the low speed jet. You can get it set close in a bucket, but for best results you need to set it after the motor is warmed up and running on the lake/river.

Let us know if that fixes it. You may not be out of the woods.

 

[joho5]

Re: Here we go again Johnson 20 hp

with it dying after reving it up, it could be your idle adjustment isnt set high enough...now your engine should be able to idle down with the butterfly completely closed in the carb, but sometimes when you rev it up and immediately idle it down to nothing, those motors can be moody and die.

make sense?

 

[HybridMX6]

Re: Here we go again Johnson 20 hp

It sounds like you may have found the problem. It was running lean and that's what caused the knocks and sneezing. Intial starting point is usually 1.5 turns out on the low speed jet. You can get it set close in a bucket, but for best results you need to set it after the motor is warmed up and running on the lake/river.

Let us know if that fixes it. You may not be out of the woods.

Glad that helped and seems to be the problem. As said above, you can get it pretty close to perfect at home, but to get it perfect you need to be on the water, with the motor fully warmed up.
I know this doesn't pertain to your specific motor, but one thing that affects mine now (2000 55hp tiller) is being in tilt for shallow water. If I have it in tilt to get across shallow water, the back pressure is different, and my motor will idle way too high to be useful. I have to manually adjust it whenever I use it like this. Thankfully, it's just a knob on the end of my tiller handle, as opposed to having to lift the hood and all that. Just something to keep in the back of your mind should you ever encounter it.

 

[jamesh76]

Re: Here we go again Johnson 20 hp

Yea, I cant wait to get it out on the water. I know it was warmed up in the barrel, but i am sure it is also different out there in the blue.

As for when I will be able to take it out......Hopefully soon. The weather is calling for 6-10 inches of snow here in Eastern Kansas. Hard to imagine that the other day my son and I were out in what we call the midget (10ft flatbottom) on a pond catching bass and crappie with t shirts on and not it is about to snow.