1989 Johnson outboard will idle and drive slow but cannot accelerate

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Devin123

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Jun 21, 2013
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I have a 1989 120 Johnson outboard V4 that I just bought and am having a problem with it. I took it out for a ride, the motor worked perfect for about 30 minutes and then a loud buzz came from my shifter for a couple seconds. After that the motor would idle fine and run fine at low speeds but if I tried to accelerate the motor would chug and shake. I also tried high idle in neutral and it still chugs and shakes.
If anybody has any ideas or suggestions it would be greatly appreciated.

Thanks
 
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Hvymtl

Petty Officer 2nd Class
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Jun 6, 2011
Messages
147
Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

Devin123 said:
I have a 1989 120 Johnson outboard V4 that I just bought and am having a problem with it. I took it out for a ride, the motor worked perfect for about 30 minutes and then a loud buzz came from my shifter for a couple seconds. After that the motor would idle fine and run fine at low speeds but if I tried to accelerate the motor would chug and shake. I also tried high idle in neutral and it still chugs and shakes.
If anybody has any ideas or suggestions it would be greatly appreciated.

Thanks
Click to expand...
Had same problem with my 90. Buzzer is overheat alarm. Turned out engine was overheating and going into a factory "limp/safe" mode where you are electronically limited to not exceed 2500 RPM until the engine cooled. My thermostats were both corroded shut. Not 100% sure you have same exact issue since we have two different HPs but a good place to start.
 
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Devin123

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Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

Hvymtl said:
Had same problem with my 90. Buzzer is overheat alarm. Turned out engine was overheating and going into a factory "limp/safe" mode where you are electronically limited to not exceed 2500 RPM until the engine cooled. My thermostats were both corroded shut. Not 100% sure you have same exact issue since we have two different HPs but a good place to start.
Click to expand...

Thanks I didnt even think of that being the problem. Do you happen to know where on the engine I would find the thermostats?
 
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hardwater fisherman

Lieutenant Commander
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Mar 19, 2010
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Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

you have one on the top of each cylinder head facing to the rear.
 
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Devin123

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Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

hardwater fisherman said:
you have one on the top of each cylinder head facing to the rear.
Click to expand...

Thanks alot for the help guys. I ran the boat for a few minutes and one thermostat heated up way faster than the other. I am guessing this could be the one causing the problem. Also the water stream coming out the back doesnt seem to have alot of pressure. I'm thinking I might also need to change the water pump. Any ideas?
 
itsaboattime

itsaboattime

Senior Chief Petty Officer
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Jul 4, 2007
Messages
791
Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

Since you just bought it, a new water pump is a good idea. That way you know for sure you have eliminated it as a possible issue. T-stats(vernatherms) aren't that expensive and are probably a good investment as well.
 
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Devin123

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Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

Thanks I bought the parts and will be putting them in tomorrow..hopefully that fixes the problem. The guy who sold me the parts also told me I should remove the oil injection system because they are not reliable. He said to do this I have to buy a new fuel pump and just mix my gas manually after. Does anyone know if theres any reason why I can't just plug the oil injection port and use the fuel pump thats on the motor now?

Sorry for all the questions I'm new to the whole boating thing I appreciate the help though
 
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cooterdude

Seaman Apprentice
Joined
May 27, 2010
Messages
33
Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

the fuel pump that is on the motor now is part of the oil fuel mixing system i dont think it will work woth the oil feed line pluged
i have a 50 horse that is pretty much doing the same thing it will run great for half the day and when i turn around to head home it goes into limp mode only goes to 3000 rpm its like it doesnt want to go home lol
 
Otte

Otte

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Jul 26, 2011
Messages
273
Re: 1989 Johnson outboard will idle and drive slow but cannot accelerate

cooterdude said:
the fuel pump that is on the motor now is part of the oil fuel mixing system i dont think it will work woth the oil feed line pluged
i have a 50 horse that is pretty much doing the same thing it will run great for half the day and when i turn around to head home it goes into limp mode only goes to 3000 rpm its like it doesnt want to go home lol
Click to expand...

I have a 1989 Evinrude 50hp with VRO that is behaving the same way too. I think I have it narrowed down to the fuel pump. I checked the primer diode and it falls within specs. I don't see fuel inside the engine cover so I don't think the fuel lines are leaking. If I do a new fuel pump I think I will go with a non VRO and mount it on the fuel side of the engine. Apparently some where in this forum there are explanations about how to do this operation... I just can't find them.
 
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