Corroded drive pulley problem?

[russp]

Hi all,
I am seeking to find out if anyone has had experience of their drive belt being ground into fine rubber powder and why. My yacht (Avalon, ex Kuchina) has a Balmar 100A alternator and runs the normal M35 3/8" belt and has done hundreds of hours with no problem.
Recently two things have been happening, firstly, the raw water pump has developed a slight leak (about to change it over, replaced seals once and still leaks at the weep hole) and the weep hole is above the alternator belt, so that the occasional drops of salt water drip onto the belt and run down the belt to the drive pulley. I have used wet and dry on the pulley to remove obvious surface rust but it is now slightly pitted.

Secondly, the drive belt started to put ground rubber all over the alternator and engine surrounds so I figured the belt was failing and replaced it after cleaning up the whole front of the engine and sump. To my dismay the new belt (correct size) immediately started creating rubber dust as well.

I am confident it is not an alignment problem as I have done over 500 hours with everything where it currently is and no problem. So I am attributing the ground rubber to the pitting on the pulley faces of the drive pulley and thinking I now need to get a replacement pulley and change over.

Any comment about, or experience of this very welcome.

Cheers
Russ Peel Avalon Hull #150

[wolfe10]

Russ,

While it is true that enough pits would reduce the belt to pulley area, that is not my first guess.

Have you verified that the the water pump and alternator are free turning with the belt removed? Belt dust can be a first symptom of a bearing failure in a belt driven component.

An old trick is to take 220 grit sandpaper and, using a Popsicle stick sand each pulley belt contact surface RADIALLY (perpendicular to belt) to give more "bite" to the pulley.

Does this happen only when the over-size alternator is charging deeply discharged batteries (i.e. high pulley load) or all the time?

Also verify that both alternator mounts are good and tight. I have seen the lower mount loose and it looks good at rest, but allows the alternator to cant sideways a little under load.

And, it wouldn't hurt to use a metal straight edge to verify pulley alignment.

[R.B.]

Is the dust only around the belt area or covering the whole engine area? You will get black rubber dust from a failing damper plate too.

If it is around the belt area, I would be looking at Brett's suggestions. Especially the alternator. Some of the high output alternators require 2 belts, so if your alternator is harder to turn (bearings starting to go) then the resistance may be too much for your single belt.

[russp]

Many thanks to those who responded, and spot on, I was jumping the gun on the cause. In fact the inner bolt on the Balmar adapter was loose and the alternator wasn't locked tight like I thought it was.

While tightening it I also took the opportunity to run emery radially over the alternator pulley faces, and cleaned off the rust on the crankshaft pulley. Then I put more tension than previously on the belt when I tightened it so that it is at the lower level of the deflection range (I don't have a guage, just guessing 10 kg pressure on the midpoint of the belt). And hey, guess what? No dust in test run for 15 minutes.

I have interesting situation (maybe common) that Balmar never actually runs hard because the regulator senses battery voltage at the alternator output terminal, and voltage drops (+ve and -ve leads) from there to battery means that the alternator always sees a higher than actual battery voltage and backs off the charge current. I don't see much over 60 amp even with an 11.5V battery, the regulator is seeing 13V+. You might ask "why bother with the Balmar?" - it was fitted by previous owner so I had no choice, but at least not running at full 100A has probably avoided belt problems and need to upgrade belts!

Regards
Russ Peel
Avalon #150

[wolfe10]

Russ,

Glad you found the loose alternator mounting-- a common cause of belt slipping.

Consider upgrading (upsizing) the charge wire from alternator to batteries to get more of your alternator's output to the batteries. Do you have a smart regulator and is it properly programmed for your battery bank? Did you move the regulator's sense wire to the batteries?

And don't overdo the belt tension-- a good way to pull bearings out of an alternator or water pump.

Brett

[russp]

Thanks for thoughts Brett. I still have about 10 mm deflection mid belt so hopefully isn't too tight, I didn't lever the alternator out, just pushed hard by hand.

Re the cables, yes, I have considered upsizing or parallelling the positive and earth cables between the batteries and alternator, and yes I have a smart regulator (Balmar) and it does tap the voltage at the alternator. With a significant voltage drop at even 60A across the cables I was reticent to move the tap to the battery and confuse the controls even more.

In the end I figured a lazy 60A out of the Balmar is probably good enough, I have 80W of solar too, what I really need to fix is the fridge, as with all C350s it is the major consumer of power on the boat.

BTW, I used to have an older style 18" LCD TV and set top box and together they drew 5.8A. I just replaced with a modern, cheap, 22" LED TV with built in DVD and HD tuner (A$189) which now draws just 1.5A so I have another 15-20AH per day up my sleeve too.

Regards
Russ Peel
Avalon #150

[wolfe10]

Russ,

My answer would depend COMPLETELY on how you use the boat.

If you do a lot of anchoring out AND use the engine/alternator to charge the batteries, alternator/battery performance becomes much more important. If that is what you do, then your primary objective is to shorten engine run time for just charging the batteries.

To achieve that, indeed sister the existing alternator to battery wire or replace it with a larger gauge one. And absolutely, run the voltage sense wire to the batteries. Remember many installations used a diode-based battery isolator which reduce voltage by .7 VDC. So on those, a sense wire on the battery side of the isolator is irtually mandatory.

I suspect your ground wire to the engine is already adequate, as it must service the engine starter as well. So if the connections are clean and tight, that should be sufficient.

BTW, we are running the same setup as you and have it wired as posted here. I watched the Link 20 before and after these mods (large gauge alternator to battery wire and relocated sense wire for the regulator). The mods significantly reduced engine run time for battery recharge and increased amps to the batteries.

Brett

[russp]

Well I had thought I had solved the problem but I hadn't, belt continued to powder, largely at the alternator and finally following Brett and others suggestion I put a straight edge on it once the mounting bolts all pulled up tight and sure enough a significant out of alignment in direction you might expect, pulled inwards by belt tension.

I have dismantled the mounts and while nothing visibly wrong, there is a bit of play in the bolt hole at the rear of the bracket where the bracket fixes to the engine block and I am hoping that is where the misalignment is starting. If not, it may be wear in the bore of the mounting frames on the engine or alternator, or wear on their faces, and that will get complicated. I have ordered a new bracket from Westerbeke and am keeping my fingers crossed that a new bracket with square faces and tight tolerances will get things working again.

Thanks for all the helpful suggestions from various persons.

I have checked re whether loading of the alternator is the problem and it is not, the batteries are near fully charged and are drawing about 20A when engine first starts and down to 10A or less within a few minutes so it is alignment and not excessive force that is the problem.

Russ Peel
Avalon #150

[wolfe10]

Russ,

Glad you found it. A common cause of belt wear.

And, another option to replacing parts is to have a machine shop drill oversize and install a bushing. Particularly helpful if you need to slightly move the hole for better alignment.

Brett

[russp]

Hi Brett,

Boy, I wish you were my neighbour on the same jetty!

I had thought about correcting the misalignment by a slightly off-line bush, but how on earth would you work out how much off-line to drill the hole and install the bush? I guess you just start with the smallest offset you can deliberately drill and hope it is about right?

Regards
Russ

[wolfe10]

Russ,

I have seen where both front and back mounts were just a little worn and the combination of "wallowed-outness" allowed for misalignment. Rebushing both back to center/tight fit on the mounting bolt(s) cured the issue.

So, if both are a loose fit for the bolt(s), I would start by rebushing to tight fit one end and then see how the alternator aligns then.

If only one mount is wallowed out install a front or rear bolt (the one not wallowed out) and then play with the offset needed to bring the pulleys into line. Use a mirror to see how much of that bolt is offset to get alignment perfect. One or two thousandths of an inch is not going to be critical.

Brett