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

[chs marine service]

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.

New video by Paul Evans

photos.app.goo.gl

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

 

[Chris1956]

That "bushing" looks like a bearing to me, although I have not looked it up on the parts list. You might see if it turns, as it appears to be pretty rusty.

Perhaps the driveshaft spins and the bearing doesn't?

 

[99yam40]

should be a bushing, clean up the drive shaft and put some waterproof grease on the shaft to keep the rust away and the bushing to lube it.
I bet your owners manual calls for lube from time to time.

but I do not know how that would cause a knocking noise

 

[racerone]

Looks to be a bushing and it appears to be water lubricated.-----Checked the gear oil in lower unit ?-----Hit a submerged object at speed ?