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knocking sound in lower section of engine cowl, above lower unit.

C

chs

Contributing Member
i have this 2013 yamaha 90hp that has a knockign sound in the area above the lower unit, i recorded it an here is a video.

photos.app.goo.gl

New video by Paul Evans

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i pulled the lower section and the noise is no longer present and i spection found that the driveshaft is
1: rusty
2 has a very shiney spot about 6.5" up which corrospinds to the area that a bushing sits in the upper unit

do you think the rusted driveshaft should be addressed? do you think replacing the bushing will resolve the knock? do you think the shiny area on the shaft indicates the shaft is smaller from the wear?

thanks for any help on this


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The driveshaft rust is normal, can you reach up inside and feel if the bearing can spin if you stick your finger in it and twist back and forth? Doe's it feel rough or bumpy when you rotate it? If it's lock up that may explain the polished look on the driveshaft. I never could understand why Yamaha felt the need to add a bearing there but maybe I'll learn something new.
 
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