Alternator belt dust

sailaway78 · May 31, 2011

Belt dust

Have pondered this problem for a while. Previous boat didn't seem to have this problem, but current one does. Have done everything I can think of to no avail. Checked the alignment, changed belts, tried different tensions, but nothing seems to help. FWIW, after a few years, doesn't seem to have any adverse effects on the alternator.

walmsleyc · May 31, 2011

I have this problem as well. Make sure that your pulleys are clean and smooth. A little bit of rust or rough surface in the inside bearing surface of the pulley can help generate belt dust faster than usual.

Another good reason to not only reduce the tension of your belts during the winter, but to remove them. Leaving them on can easily result in just a little bit of rust/corrosion between the belt and the pulley.

WARNING: Dangerous operation being discussed.

While the engine was running, I very carefully used some fine emery paper on the end of a stick to polish the surfaces. Since doing that, I have had almost no dust. Obviously, this could easily lead to the loss of your fingers if done improperly. You can also do this with the engine not running by manually spinning the pulleys, to a very reasonable effect, and significantly less dangerous.

Chris

kloudie1 · May 31, 2011

Woah, Chris.. if I loosen my belts in the winter, they make more dust .. and if I remove them, the thing overheats !! ?? ;~)

RAD · May 31, 2011

kloudie1 said:
Woah, Chris.. if I loosen my belts in the winter, they make more dust .. and if I remove them, the thing overheats !! ?? ;~)

Just keep rubbing it in about sailing in the winter

kenn · May 31, 2011

One thing pointed out to me by my mechanic friend was that the Japanese belts on a stock Yanmar often had a different angle of bevel than North-American off-the-shelf belts... so if you replaced belts without matching the bevel, you'd get more shed. Likewise if you upgrade to a Balmar alternator, but the Balmar pulley doesn't match the stock bevel of the rest of the components.

The shed is messy, but the biggest issue with a mismatch would be premature failure of the belts.

Ray Bowles · May 31, 2011

Belt and sheeve groove angles differ, not alignment.

I will try as best possible to explain this quite technical response to this posting without the advantage of pictures. The figures used are for iillustration purposes as I can't remember the original numbers.
If you have the sheeves lined up so the belt has absolutily no alignment difficulty then the following might help identify your problem.
There are different sheeve side angles that cause mis-matchs for belts. Many mechanics do not see these differences and install incorrect belts. The sheeve (pulley) sides have different angles that run from the top sides down into the base of the sheeve (60 degree,65 degree, etc.) They also have different widths at the top vs the bottom. These differences are identified by belt types, a-belt, b-belt, etc. You can't run differently angled sheeves and expect the belts to last. The identifier of most of these mis-matches is alot of belt dust. The belt dust, unless very excessive, usually won't harm the alternator. It will rapidly eat the belt and more so if the batteries are low. This loads the alternator belt excessively.
I found that I needed to take my sheeves to a Gates belt and hose warehouse to end up with the right belt. My Yanmar 43 hp engine had the stock factory crankshaft and waterpump sheeves but the altenator pulley was wrong. This caused excellerated belt wear. The previous owner had installed a different alternator with a different sheeve sides. After installing the correct altenator pulley the condition never reappeared.
You can also try to bribe a VERY good counterman or mechanic to measure your sheeves on the boat, in the water, to identify you belt needs.
Possibily Maine Sail can help explain this condition.
Ray

RAD · Jun 1, 2011

I would think that there's a sheave angle tool or a simple way to measure it

RichH · Jun 1, 2011

J&R -
IF this is a Yanmar engine, the crankshaft sheeves and especially the pressed steel Freshwater cooling pump sheeves are NOTORIOUS for rusting, especially during a long layup. To prevent this 'rust bloom' during long term layup, simply spray the shined-up sheeve surfaces with "Boeshield™".
The best (and safest) remedy for rust blooms on the sheeve faces is to remove the sheeves and take them to a machinist to have them 'dressed' back to smooth (and true). Just remove the three bolts on the FWC sheeve to loosen. Remove the crankshaft 'nose bolt' which restrains the crankshaft sheeve and the 'whole assembly' will slide off .... dont lose the 'key' when removing. Trying to 'shine up' vee groove faces by holding a 'stick' with emery cloth when the engine is running ..... is a damn good way to lose a finger or two.

If the sheeve grooves are 'bright and rust free' and the pulleys, especially the alternator, is in perfect alignment then if you have an external 'smart' regulator you can slightly 'de-rate' the power of the alternator OR its 'ramp-up' interval (regulates how 'fast' the alternator 'energizes') .
If the alternator is 'ramping-up' too fast this will also cause significant 'belt dusting'; decreasing the ramp-up by adjusting the 'regulator' (how 'fast' the alternator 'energizes' - can cause belt slip during the 'ramp-up') will allow a 'softer' ramp-up to full alternator load - usually a 'last resort' for belt dusting problems. The max. 'load' on a standard 1/2" belt will be about 100 amps draw on an alternator and the belt will slip (causes 'belt dust') especially in variable alternator loads.

Summary of belt dusting:
1. misaligned alternator
2. sheeve / vee-pulley roughness (surface rust)
3. belt at or beyond maximum power transmission load ( ie.: single 1/2" belt running a 100 amp. alternator)
4. Alternator 'energizing' too fast (ramp up).

Use a belt tensioner gage (NAPA, etc.) when setting belt tension.

Roger Long · Jun 1, 2011

RAD said:
I would think that there's a sheave angle tool or a simple way to measure it

I had an OEM Yanmar belt and the NAPA belts I've been using in my spares kit so I measured them carefully.

The Yanmar is the smaller, red(ish) outline. I've had lots of dust but also horrible alignment due to a bolt which came loose and enlarged the mounting hole which I have corrected. We'll see how it goes now.

Bill Roosa · Jun 1, 2011

You do know that there are two shapes of "Vee" belt right. As you found there is a narrow Vee and a wide Vee. the two can be used on the wrong pulley in a lot of low power applications. Alternators is not one of them due to the small diameter of the pulley and the amount of power you are transfering.

zeehag · Jun 1, 2011

my perkins belts dust frequently until i had a loud noise on startup-- both alternator mounting bracket bolts broke in one swoop--lol-- try your alternator bracket readjustment or wait until the damn thing breaks as did i-- i am having a new bracket made for my alternator so i dont have to vacuum belt dirt off my engine anymore--LOL.... goood luck.
tomorrow i have my bolts easy - outed from block and start over with fabricated stuff all new to me. life here in mazatlan is goood-- stuff is cheap to repair ..LOL

Roger Long · Jun 3, 2011

I went to the Yanmar dealer today to get a new belt. He was very familiar with the problem but said that Yanmar lists all their belts by engine model not by length. If you change something like the alternator or the pulley, you are out of luck without going through all of them one by one.

He said I could go to NAPA and the would measure the bevels and length and set me up with the right belt. I did, they measured and checked, and the closest thing they could come up with was a skinny little green belt of about half the cross section. They tried Yanmar cross reference and a few other things. Now that I have a slightly larger alternator on my engine than the stock one, it looks like the semi-fit NAPA belt is my best option. They tried Yanmar cross reference and a few other things.

There should be less dust now that I have it properly lined up but there probably still is going to be some.

kenn · Jun 3, 2011

Roger Long said:
I went to the Yanmar dealer today to get a new belt. He was very familiar with the problem but said that Yanmar lists all their belts by engine model not by length. If you change something like the alternator or the pulley, you are out of luck without going through all of them one by one..

I would expect that even with an alternator change, there would still be enough range of adjustment with the stock belt, especially if you move the stock pulley from the replaced alt to the new one. I did at least one of those last year (Balmar alt onto new Yanmar engine) and the stock belt was reused.

Rick D · Jun 5, 2011

I went through the same thing with mine "He said I could go to NAPA and the would measure the bevels and length and set me up with the right belt. I did, they measured and checked, and the closest thing they could come up with was a skinny little green belt of about half the cross section."
I had it on for 500 hours before replacement for service reasons only and it had held up just fine. The Yanmar belt dusted a lot compared to this one. I was a bit skeptical because of the much smaller amount of material, but it did a fine job. Replaced with the same & I carry a spare. PS: I have a Balmar too. It runs under big load pretty often.

Roger Long · Jun 5, 2011

kenn said:
I would expect that even with an alternator change, there would still be enough range of adjustment with the stock belt...

No, the new alternator was larger in diameter than the stock one. With it hard up against the engine block, there wasn't enough slack to get the original belt on.

Roger Long · Jun 5, 2011

Rick D said:
I had it on for 500 hours before replacement for service reasons only and it had held up just fine.

You mean the skinny green NAPA belt?

Rick D · Jun 5, 2011

That's it if it's toothed on the inside.

Roger Long · Jun 6, 2011

Rick D said:
That's it if it's toothed on the inside.

The one they showed me wasn't. I've been running the NAPA toothed belts and which are the ones with a slightly different profile as shown in the post above. The outline I drew doesn't indicate the cut outs for the "teeth".