Pulley alignment

[Bill1565]

I have "belt dust" all over the front of my engine. Have about 150 engine hours on the boat since we bought it. Bought 2 x spare belts when I first noticed the rubber dust, but haven't broken the belt yet. I have a steel straight edge, but it flexes sideways.

Any good thoughts on how I can check pulley alignment?? Any thoughts on aligning water pump or drive pulley. I know I can bend the alternator mount, but I don't know if that is the problem, nor which way to move it.

 

[Maine Sail]

Often times the case to pulley dimensions on a replacement alts are not the exactly same dimensions as the factory alt thus throwing off the pulley centering.



To combat this I often machine off some of the alternator mount ear and then use shims to move it fore or aft depending which way it is off. You are far better to align the alt to the rest of the pulleys.



If you google alternator shims you can sometimes buy them pre-made but they are often copper which I don't tend to like next to the aluminum. Just use a piece of flat granite and some wet sand paper and shave aluminum washers to the right dimension. You want a snug fit between the alternator mount ears so you don't fracture the mount by over stressing it and bending the ears in. Many of these brackets are cast steel, aluminum or iron and snap rather than bend so go for a good tight fit with your shims.



I have installed many alts on engines and not had an issue once the pulleys were lined up. You can hold a straight edge/ruler flat to the machined face of the alt pulley, not he floppy way, then use calipers to measure the distance to the belt at the alternator end. Then move the calipers to the pump end of the belt and see what the difference is.


You may also have rusty corroded pulleys that chew up the belt..

 

[RichH]

You may also have rusty corroded pulleys that chew up the belt..

If you have a Yanmar engine, the pressed steel FWC pulleys/sheeves are notorious for rusting/pitting - and once the sheeve faces become roughened you will get 'belt dusting'

If your alternator is at maximum load and has a 'simple' or single stage voltage regulator, the dusting may be the result of the alternator energizing 'too quickly' causing momentary slippage of the belt as the the alternator 'ramps up' - dusting. The correction to this is to apply a 'smart regulator' and slightly 'de-rate' the alternator output and/or the 'ramp up' timing (the time interval that the alternator 'energizes').

The choice of belt manufacturer also has a lot to do with belt dusting, especially when alternators are at full load -- sometime just a change to a 'premium' brand of belt will alleviate dusting -- Gates or Top Cog are typically the best belts to use.

 

[Old Skool Neil]

I like to examine the belt for signs of wear. If the edges of the belt are damaged or frayed you should look at alignment or belt width vs. pulley width. If it's the bottom of the belt cross section that's damaged, the narrow part of the Vee, the internal surface of the pulleys comes into play.

 

[Witzend]

I had a hose clamp that was interfering and causing some dust, make sure the belt path is clear when running.

 

[Bill1565]

here is the belt

You can hold a straight edge/ruler flat to the machined face of the alt pulley, not he floppy way, then use calipers to measure the distance to the belt at the alternator end. Then move the calipers to the pump end of the belt and see what the difference is.


Help! I don't understand what you said Maine. In my mind, doing as described will measure /compare pulley wall thicknesses.

I went back to the engine room, looked around and took a lot of cell phone pictures. two came out ok. In the photo of the alternator pulley, the belt looks to be down in the groove further than the other pulleys. feels like 1/16 or better of pulley above the belt. Belt wear seem confined to very widest part of belt. I vacummed and wiped engine as well as I could. Will watch for new dust, althoug we are in day sailing , mode till at least the 22nd. won't put many engine hours on clearing the canal.

Sorry, photo of dog was for another thread. Will work on deleting it