What is this "dust" ? - F225 camshaft gear

[fairdeal]

2005 F225TXRD

a reddish-brown "dust" collects on the top of the port side camshaft gear

I've wiped it off several times, but it's back after a few hours of running.

I can't see any obvious signs of "rubbing" anywhere to generate dust...


Anyone know where this "dust" is coming from?


an additional mystery -

the starboard side gear is always spotless -

must be some difference in electrostatic charge? air flow inside the cowling?

[TownsendsFJR1300]

It may just be the pic angle, but it looks like the "center star" has moved from the pully. (I would think its cast as one piece).

Did you check the torque on the cam / pully bolt?


The parts fisch shows it as one piece; http://www.boats.net/parts/search/Ya...LVE/parts.html


However if it isn't cast as one unit, again, it appears the two separated.....

Lastly, the belt tensioner, part #22, how's that look/ roll?(any roughness, bearing disintegrating?)

[fairdeal]

Thanks for the suggestions, Scott

There IS a lot of angle to that photo - actually the top of the gear looks fine

except for the "dust"

I haven't removed the bolt - so I can't speak to the torque - but it, and all the other parts of the belt pathway, are "tight" to the touch

including the idler. Which looks, feels and sounds good.

I'll be replacing the belt (although that also looks "new")

but it would be nice to understand what's causing this....


I was hoping this might get some input from Rodbolt.

He must have seen these engines 1000's of times

here's a photo from a different occasion - not long after I completely cleaned the pulley...

[DennisG01]

To my uneducated eye, it just looks like belt dust, no? For whatever reason (you mentioned a few), it collects on that pulley and not the other.

[TownsendsFJR1300]

I gather the plastic top cover isn't rubbing? It does looks like something, metal to metal not tight and the rust spraying out...

I'm sure RB will chime in, curious too....

[fairdeal]

"belt dust" ?

just fine particles of the belt itself, generated by flexing / internal friction?


The rubber doesn't seem particularly "dry" or "brittle" but

AFAIK this is the original belt - installed by Yamaha almost 11 years ago

so, maybe that's it

since there's no sign of "rubbing" anywhere.


Well, I'll be installing a new belt this week -

I'll report back after I've got a few hours on it

thanks, guys!

[robert graham]

I'll bet Rodbolt can shed some light on this red dust mystery....strange it's on just one pulley?????........

[TownsendsFJR1300]

I'd find the torque spec for that cam to pulley bolt and check it.

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...

Good luck and please post what you find...

[rodbolt17]

looks like either belt dust or the tensioner pulely is failing. best I recall Yamaha recommends belt replacement at 1000 hrs OR 5 years whichever occurs FIRST.

[fairdeal]

thank you, Rodbolt!

turning by hand, tensioner feels silky smooth & silent

so hopefully its just the belt


I haven't been worried about the belt's age

knowing its not an "interference" engine -

(and I pay for unlimited TowBoat !)


but I'm putting a new one on now

[rodbolt17]

never saw a tensioner bearing fail but we do see the damping fluid leak out and it turns a reddish tint.

[fairdeal]

aha - I will look for signs of that.

There doesn't seem to be any loss of damping "performance" -


its not very satisfying trying to "relax" that idler.

(I've seen a bulletin warning to use no more than 11 ft/lbs to swing it...)

I assumed I'd be moving it enough to get some "slack"

but I'm seeing just enough reduction in tension to get the belt to slide up

[TownsendsFJR1300]

Solved, cam gear gone south..

http://www.yamahaoutboardparts.com/f...tml#post111767

[fairdeal]

thanks for "closing the loop", Scott

I just found the photo below via Google images-

obviously this is where mine would eventually end, if I ignored it!

[TownsendsFJR1300]

Its a good thing you noticed it and didn't ignore it.

Please post back if that lower RPM noise goes away with the old pulley(I'd think so..)