rusty pulley

duncan

duncan

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the main crankshaft pulley has got rusty on the front of my Yanmar (4LHA) and fo rthe last season it has been rust 1 belt 0 resulting in a fine sprinkling of black dust (and no doubt excessive wear to the belt!).
Like many I am currently 'looking for jobs to do for the next month - most of which will still be on the list next year if the sun comes out before June - and sorting out this pulley seems a good candidate.
How would you proceed? Sanding the rust off or shot/sand blasting the pulley will leave me a beautifull clean bare metal pulley that will rust again in no time but what are my alternatives?

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My first thoughts are that:

a) where the belt is in contact with the pulley, then it will always get rubbed bare, and if the engine is used regularly then little rust should have a chance to form. Any surface treatment would be a waste of time as it will be rubbed off by the belt.
b) Any surface where the pulley is NOT in contact with the belt, could be treated with one of the many anti-rust remedies / paints.



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it happened to me as a result of standing for some time between installation and launch, also over winter. a rub with fine emery paper (with engine stopped!!!) fixes it pdq but it will come back each winter.

any anti-rust treatment is likely to make the belt slip.

once you've cleaned up the pulleys, fit a new belt as the old one may well have worn thin enough to be bearing on the bottom of the groove instead of the sides.

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The crankshaft pulley on my yanmar 2GM20 frequently develops rust on it during long periods of disuse.
It always polishes up within a few minutes of running the engine.

Your problem sounds more like one of insufficient belt tension than anything else.

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Agree....

...with you and Charles.

This sounds like the alternator slipping to me too. You may soon also get charging problems.

Most belts (on Volvos & Yanmars) require a deflection of 3/8" or 10mm along the longest run between pulleys but check with your engine handbook first.

Any rust on the inside faces of the pulleys will soon disappear after a few minutes running.

Steve Cronin

<hr width=100% size=1>The above is, like any other post here, only a personal opinion
 
Don't know your engine but I had a lot of problems in the past with chewed belts and black dust and the problem was a belt alignment one - the belt was a polyV though and probably easier damaged than a standard V.

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fish oil? wd?

really!! no professional that ever worked for or with me has ever done anything so daft!!
check alignment, check tension, check the v isnt bottoming in the pulley.
thats it, simple.
stu


<hr width=100% size=1>http://www.beneteau-owners-association.org.uk
 
This not an uncommon problem in the Motor trade where a punter has bought a second hand alternator from the scrap yard which has a heavy layer of rust on the pulley. Once the pulley surface has got severe corrosion on it there will be a very abrasive face for the belt to run on and so lots of dust and eventual failure. At the very least you have got to change the pulley.

Ted.

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I had same on Yanmar 3GM when I got the boat. The rust looked so bad I bought a new crankshaft pulley but I couldn't get the old one off so filed and sanded it and it's been fine for 5yrs now but with regular running - at least once a week for about 45 mins and obviously more in season. I can't see any problem hazing a bit of WD40 or similar over the crank pulley if belt is at right tension particularly if the engine isn't going to be used for some time.

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Re: Agree....

yep it is 10mm Steve and set right, and aligned ok. The pulley got a little salt water on it (as a result of the last time I let a professional onboard) and has gone rusty outwith the shiny area where the v belt sits. Maybe a little movement in the belt causes v occasional rubbing of belt on a rusty spot.
I will clean up the pulley and repaint outwith the nice shiny area then monitor.
The WD40 will continue to be used on conger and tope baits.../forums/images/icons/smile.gif

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