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30 hp Johnson runs rough at half to full throttle - help needed

Eric McDonald

New member
Hi everyone,

I inherited my father's 30 hp Johnson, I believe it was made in approximately 2000. It has been in storage for a decade. Yesterday I took the boat out and the motor ran great to begin. Started right up. Ran smooth for about 45 minutes at low and wide open throttle. I shut it down for the kids to swim and when I started it back up it ran fine at low throttle but really rough at approximately half throttle to full throttle. If I would back off on the throttle it ran fine at low throttle again. Here's a video of it.... the rough running starts around 15 sec: https://youtu.be/__wv8NXOENU

The engine has low hours. The gas was fresh and mixed 50:1. New fuel hose installed from the tank to motor.

What should I try to fix this? And in what order?

If I have to take this to a repair place, what do you expect it to cost?

Thank you for any and all help!
-Eric
 
was fuel tank cleaned, inspected for debris,could be debris in carbs by now,possible air leak in fuel line,clogged fuel pickup tube in tank,
 
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