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johnson 25hp vibrating violently.

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leeroy80

New member
Hello everyone,

I am new to this boating/ forum thing so please bare with me. I have a 1985 Johnson 25 hp model: J25ECOC.* This thing fires right up and idles great. My problem is when I run faster then about 5 knots the motor starts to shake violently all the way to wot. It does not bogg down it will accelerate and shake the entire boat all the way to full throttle. I played with the low speed needle at full throttle and I can get it to run perfect with more power (sounds healthier too) when the needle is basically all the way closed. I didn’t do this for long since I know the damage it can cause by running too lean. This makes me think that it’s something with the Carburetor since I can adjust it to normal operation. Maybe an air leak or a stuck float? im not sure. I am pretty handy and plan on working on this myself just have little experience with outboards. Anyone ever encounter this issue? No idle problems.
 
thank you for your reply.
I actually had a different prop on there before and it would do the same thing. I have a feeling it's in the carb since closing the low speed needle makes it run normal. the motor will shake at any other needle setting. it's due for a cleaning I plan on taking it apart next weekend when time allows. I'm just scared of leaving the needle closed all the way all the time since it may run too lean. am I on the right track?
 
The needle is for the slow speed mixture only!-------So if it really has an affect at full throttle then I suspect carburetor problems.--------Take it apart and have a look see.-Inspect fuel pump diaphragm too.
 
Concentrate your efforts on the carburetor !-------------But check your lower unit oil for metal bits / contamination.--------And perhaps check the condition of the flywheel key.
 
thanks for all the help. I have some time this weekend and will be checking some of this stuff. I will also redo the carb with a kit. thanks for your replys
 
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