Johnson 150 running issues

jasoncooperpcola

jasoncooperpcola

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Today i went to run my 1985 Johnson 150 on a 6 gallon tank with fresh gas and it wouldn't run below 1000rpm. If i turn the choke knob it will run rough below 1000 rpm. When i hold the carbs open a little it will crank and run beautiful. I try to run this motor once a month on fresh gas with stabil in a small tank but its been three months since i have run it. Tomorrow i plan to check plugs. What else should i check? I am beginning to think its a carb issue. I do not know when they were cleaned last. Right now i have adjusted the throttle cable out so it runs good. But i hate to cover up a problem by doing so. Anybody got any suggestions?

Also i have a 25" shaft Yamaha 150 2 stroke i may put on but need a remote control.
 
Would i need a chilton book for that? I haven't pulled the silencer cover off yet so i don't know what i am getting into. I cleaned/rebuilt all the carbs on the twin 150 Yamahas on the big boat. Is it pretty much straight forward like the yammies, where i can see the jets when i remove the silencer? Also would i need a rebuild kit with all the gaskets and such?
 
The jets that need to be cleaned will be inside the float bowls. If your careful you can normally re-use teh gaskets, but it is always a good idea to change them.
 
One thing I've found through the years is to always run any gas going into my engines through a fuel filter....even from a portable gas tank. I made up a portable fuel line that goes into a filter, and then the filter has the regular engine fittiing on the outflow side. I figure that a little protection is well worth the slight extra cost of the filter.
 
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Destroyer said:
One thing I've found through the years is to always run any gas going into my engines through a fuel filter....even from a portable gas tank. I made up a portable fuel line that goes into a filter, and then the filter has the regular engine fittiing on the outflow side. I figure that a little protection is well worth the slight extra cost of the filter.
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Good thinking, but i already have that covered. I hook my portable tank to the inlet of my Racor fuel filter. My main tank hasn't been hooked up since August!
 
I took the top carb off this morning and was amazed at what i found. Both #15 was clogged with a thick green crap. The bowl has a puke greensih film in the botom and in the passages #5 to #15. How can i clean this plastic bowl without harming it. O'reillys had nothing that would work. After seeing this i am surprised the engine ran at all. I figured i would blow everything out with compressed air. So far i have #5 #3 #15 jets from the top carb soaking in cleaner.

Below is a picture of the bowl.
 

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jasoncooperpcola said:
I took the top carb off this morning and was amazed at what i found. Both #15 was clogged with a thick green crap. The bowl has a puke greensih film in the botom and in the passages #5 to #15. How can i clean this plastic bowl without harming it. O'reillys had nothing that would work. After seeing this i am surprised the engine ran at all. I figured i would blow everything out with compressed air. So far i have #5 #3 #15 jets from the top carb soaking in cleaner.
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They should be metal on an 85 150 as that is the old style cross flow engine. As for cleaners, I use EVINRUDE engine tuner in teh gallon jug to soak them. I also have an ultrasonic cleaner that I use if they aren't that bad.
 
These are black plastic bowls. i have been soaking the jets in a carb cleaner i got from o reillys in a one gallon can. While i have them apart, what is the float drop measurement?

Below is a clean jet next to a dirty one.
 

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You can soak them in SEAFOAM for about 20 minutes and see how much comes off. DO NOT use carb dip as it will eat the plastic. I personally use EVINRUDE engine tuner in the ultrasonic dip tank.
 
i've always used a 50 / 50 mix of mineral spirits and lacquer thinner. i use that on the whole carb assembly including the plastic parts too. then blow it all clean with the air compressor.
 
There is a marine program at George Stone where i am taking welding. I am going to let them do carb kits on all the carbs and clean the bowls so hopefully there will be no more issues. After they do carb kits, they will put my outboard on the dyno and see what it puts out.
 
jasoncooperpcola said:
There is a marine program at George Stone where i am taking welding. I am going to let them do carb kits on all the carbs and clean the bowls so hopefully there will be no more issues. After they do carb kits, they will put my outboard on the dyno and see what it puts out.
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Did you ever read Tom Sawyer? :hide:
 
Update

Found out i had low voltage on two plug wires, had carbs cleaned, a few electrical gremlins with the ignition, and the shaft mounts and steering shaft are shot. Motor had 92-94psi compression on all but one cylinder which had 82. If nothing else breaks when trying to repair it, it would cost over $1000 just for parts.

So i am having another motor installed this coming week, a 1986 Yamaha 150 25" shaft. I will build a jack plate, out of some 4x4 1/4" wall square steel tubing i have, so it will work on my 20" transom. Now i just need a remote control.
 
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