D1-20 belt

[sunshine]

Hi folks,
The D1-20 on my 2006 Bavaria 30 has recently acquired an appetite for belts. Black dust in the engine compartment and visible wear on one side of the belt. On taking the genuine Volvo penta belt off and comparing it with a spare (same part no - 3809625, 197) it seems to be slightly, but noticeably thicker side to side. The wear on the belt is on the outside edge at the back ( ie engine) side. I've checked for play on the alternator and water pump pulleys and all seems fine. Placing a straight edge across the pulleys doesn't show anything obviously out of line.

So is this just a case of a batch of belts slightly oversize, or something else? Any experiences or thought would be appreciated. 

Pics attached are of the wear on the belt and side be side comparisons of two belts sitting on a flat surface. Measuring the belts, its hard to truly determine the size without vernier calipers, but the spare is about 17mm and the worn one very slightly more, maybe17.5mm.

[Yngmar]

V-belts wear on the sides of the V, so it's normal that a used belt is slimmer than a new one.

Check the pulleys for rust and polish them if need be - a bit of surface rust can easily chew up a belt. Too loose a belt or overload (e.g. if you fitted a new alternator or smart regulator) can also cause excessive belt wear. And obviously it needs to be tensioned right

[sunshine]

Thanks. Used one is slightly wider though- unused spare is thinner. Which is why I'm wondering if there's been a dodgy batch which is slightly over-size. Thanks for the hint on the rusty pulley - late start to the season means could well gave surface rust as a result of the boat sitting too long.

[Yngmar]

I see. And I also managed to look at your photos (low bandwidth at anchor here) and see it's a multi-V belt, which should suffer less from overload.

Volvo only sources these from other suppliers too, so the same part number doesn't mean that much. There might well be variances between suppliers and batches. And of course there's product fakery everywhere these days.

Personally I always buy Gates belts, they're a large automotive/industrial manufacturer, vastly cheaper and because of that, fake ones are much less likely (as it would be less profitable). Never had a problem with them. It was easy to look up which one matches my Volvo one online (different engine).

So I'd swap the belt for a fresh one from a different batch to see if the problem persists, and while it's off, check for rust on the pulleys and spin the alternator and water pump and check for bearing play to see if there's any problem there.

[Craig]

Comments above are the most common causes of belt wear.

One other problem you may wish to check is if the alignment of the pulleys is correct.

Saw belts chewed after an alternator replaced and new alternator had the pulley out of alignment by a few millimetres.

Craig
"Shirley Valentine"
Gold Coast
Australia

[Symphony]

The original Volvo belt on my D1 30 is 18mm wide. No sign of any chafing or wear.

[PEA-JAY]

Hi, I’m surprised you’re having this problem with a multi-v belt. They are far superior to ordinary v-belts. There could be a small misalignment causing the problem. Usually it’s play in the alternator mounting. Another less obvious problem is groove wear on the pulleys themselves. Normally this results in belt slip which you tend to try and overcome by over tensioning that wears the belt faster. Gates give away small plastic wear gauges with which you will be able to check both the pulley and the belt. Be aware there are loads of counterfeit parts around so make sure you’re buying your supplies only from reputable parts dealers!

[Salty]

One other thought might be bearing wear on the shaft to which the pulley is attached.

[sunshine]

Thanks everyone for their help with this. Pulley alignment is as per original, and both alternator and water pump shafts appear fine judging from no play when waggling those pulleys. I spent a bit of time yesterday and reckon its rust on the crank pulley. First pic is as was, second is after a going over with a wire brush. I'll update this post in a couple of weeks when I can tell whether this has made any difference.

[Yngmar]

That's quite rusty for a pulley. Ours had less than that and was chewing belts, so this is the likely culprit.

Easy to polish while the engine is running (there's enough open angle with the belt on). Although be very careful and don't stick your fingers in there.

[sunshine]

The underlying issue is probably using the shower. The little plastic door that allows access to the oil filter from the heads doesn't have a seal, so water ends up in the channel to starboard of the engine. I do try to sponge it out after showering but I guess there will be a level of moisture near the bottom of the engine encouraging the pulley to rust. Winter project to add a seal to the door.

[sunshine]

Ok, the actual issue here was a tiny leak in the raw water pump hose close to the pulley. Not enough of a leak to cause water to collect anywhere, but I guess enough to create a salty moistness just right to encourage surface rust on the pulley. Anyone else ever wondered why the spigots on the raw water pump are slightly too short to allow two hose clamps to be used as per normal marine practice? And why people overtighten the single clamp to compensate but end up nicking the pipe?

[symphony2]

Two clamps are really unnecessary, although common in "marine" circles, dating from the days when they first came in and old lags were suspicious of these new fangled things. Provided they are all 316 construction the likelihood of failure is almost non existent. Indeed the problem is often removing a hose from the spigot rather than the hose coming loose. How many of the hoses on your car are double clipped?

[Yngmar]

Your car doesn't sink into the asphalt to vanish forever if one of the hose clips fails though

[symphony2]

That is obvious - but where is the evidence that clips regularly fail on either cars or boats (and sink as a consequence)? There is often a big difference between imagining what might happen and what actually happens.

[sunshine]

Setting aside any argument over whether two clips are actually needed, why are bavarias supplied with water pumps that are single clipped, when everything else on the raw water side such as inlet seacock, raw water strainer, anti-syphon valve etc are double clipped? If its not needed, then everything can be single clipped. If it is needed why is it acceptable to single clip the pump?