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20 hp runs bad

J

johnstro45

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I have a 20ba77s Johnson that runs real bad. I recently bought the boat and motor. The first time I took it to the lake it started ok. It's a hand crank.
I pulled away from he dock and that's when the fun began. The motor started missing. It was running on one cylinder. The motor then banged like you hit it with a sledge hammer. It kept running. It would do this about every minute. I got it home and started checking things out. I had no spark on one cylinder. Pulled the flywheel to check the points. Ended up replacing both mags, and both sets of points. Replaced plug wires. Spark jumps a 3/8ths gap. Took the carb apart. Very clean inside. Blew out jets. Checked the float. moves free and is set to specs. Compression is 120 lbs for both cyls.
If I pull the plugs they are wet[new plugs]. It acts like it's getting too much gas. I checked the diaphragm in the fuel pump for holes, thinking excess gas
was getting in through there, pump was ok. When running at home in a tank it has excess smoke from exhaust. It runs bad in all throttle positions.
The only thing I can see that makes me wonder is while running the mag, or ignition plate wobbles up and down about 1/16 th of an inch. Don't know if that could be the problem. Could this problem be from bad reed valves? Any help would be greatly appreciated.
 
The model no. is for a 1977. This is the 50th anniversary edition. I do know when looking up parts you have to go back to 1972. I looked up the model no. on line and it also says it's a 1977. It does have points and mags. I got the model no. right off the factory plate on the motor.
The plate says it's a 20BA77S. If you look for a 20 HP in 1977 there is none. I believe it goes from 18 to 25 hp.
 
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I'm not trying to argue with anyone about the year and model of this engine. All I have to go by is what I looked up for the model no. It said it was a 77 seahorse 50th anniversary made by Johnson. As for the halfassed carb cleaning. I bought the boat from a place that sells used boats. They already put a carb kit in it before I bought it. I did use carb cleaner in case there was something left in one of the passages. I took the boat back to where I bought it and complained about it not running right. They were stumped as to why it was running this bad. I brought it back home because they were getting nowhere. As soon as it stops raining I'm going to try disconnecting the fuel line after starting it to see what happens there.
 

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Here is a picture of the mag plate, and the model # tag I checked the timing and the mark on the flywheel was in between the two marks at an idle. I disconnected the fuel line from the tank. It didn't smooth out just before it died. Checked the points.both sets are at .020. There are no grooves in the flywheel key.
 

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I did pull the needle for slow. I checked it for being smooth in case someone tightened it too tight. When I put it back in I turned it out 11/2 turns as you mention. I did start the motor and let it warm up. I adjusted the needle in gear until it ran as smooth as it was going to. I just checked the synchronization and found it out of specs. I adjusted it according to the service manual for the ignition system on this motor. I haven't tried to run it yet.
 
Boy, this can get confusing. The service manual I'm using is on line. It shows D-3 for the adjustment. I'll look again in case I crossed my eyes looking at it. After making the adjustment with the D-3 setting it did seem to run better. I did notice the cam is worn and the cam sleeve has a flat spot on it. I just ordered both parts.
I just looked in the manual again. Apparently I did cross my eyes. It is C-3 for 72. must have been looking at 71. Thanks for posting this to straighten me out.
 
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The cam has 2 notches. There are wear marks on the cam like someone ran it in one position whenever they ran the motor. After adjusting so the cam sleeve was between the marks, the throttle control had to move too far to move the throttle shaft. The cam is worn that much.
 
I gave seaway a call. I guess I have a mystery motor. They have no listing for that model no. They did tell me that if everything was working from a 72, keep doing that.
 
Johnstro45, me too I got the same engine as yours. Same model number 20BA77S.

Here is some picture of my engine.
IMG_1089_zps4720615f.jpgIMG_1090_zps37fbd515.jpg
 
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For a number of years the 20 HP was only marketed in Canada.------------------The motor that the original poster has is a 72 model painted green and the 50th anniversary year.----Likely had the transom bracket or model plate changed.
 
I tough the last 2 number was referred as the year it was made. Because the inside of my engine is exactly the same as the original poster.

By the way, my question, as the original poster, where can we get the manual?
 
The bracket is easy to change and the identification plate is easy to change.-------The paint is harder to change !!--------The motor in post 21 is indeed a 77 model as per the 77 on the identification plate.
 
Calv, I went on line and found a site called "boatinfo". They have the service manuals there for all models of boat motors. You can down load them, but for example the one for the 20hp Johnson is 600 some pages long. That's because it covers more than one model motor. I imagine you could print just the info out of it you want.
 
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