"pulley dust" - Scott nails it!

[fairdeal]

My moneys on it being slightly loose and /or the pulley hole wallowed out. Its the only place it can be coming from.

Centrifugal force is throwing the dust outwards from the center. There's a fair amount of sideways pressure from the cam belt...

Scott, as my mother used to say, "hope you don't strain your arm, patting yourself on the back"

With the belt on, there was NO "feel" of loose-ness.

With it off - rockin' and knockin' - here's a video - with sound

https://vid.me/tKUi

This is a phenolic resin gear, molded around a steel keyhole washer.

The washer was bolted tightly to the camshaft - but "working" inside the gear.

So that's what the dust is - powdered gear.

And I think, now I have a cause as well for the "hollow tapping sound" I've been hearing at idle from that area!

[SeaDawg3]

give that man a ceeegar!!!

[TownsendsFJR1300]

Excellent!!! Glad you found it!!!!

[robert graham]

Wonder what Yamaha gets for a new gear???$$$$$

[TownsendsFJR1300]

Just over $100.00, not bad for a part with Yamaha stamped on it;

2005 F225TXRD Yamaha Outboard VALVE Diagram and Parts

Part #18

[robert graham]

The red dust is a good natural indicator of that phenolic gear failing....something to look for when checking/tuning the motor...