Serpentine Belt advantages

[rgleason]

I've done some searches and have come up with this list, it would be helpful to get some confirmation on the advantages from actual users, qualitative as well as quantitative.

Serpentine belt advantages:

1. drives larger alternators easily
2. more efficient power transfer, less energy loss to belt.
3. uses less energy, more efficient, requires less HP
4. less belt tension required, better for bearings on engine and alt
5. belt tension is not as big an issue as V.
6. less slippage, less heat
7. less dust
8. quieter

Serpentine is not necessary for up to 100 amp alternators.

[Training Wheels]

Funny, I just ordered a serpentine belt conversion for my 70A alternator. Got tired of the belt dust.

[a64pilot]

I’d say 80 from just my experience is the absolute max on a single belt and only then if you don’t mind excessive tension and alignment is spot on perfect.
Why would a serpentine belt be more efficient? If it is due to tension etc., not sure it’s a big difference. For me the deciding factor was the excess tension and belt dust from a single belt.
My stock 80 would start dusting as soon as tension even approached correct, and I assume once the belt starts throwing dust, it’s worn slick and is thinner than it should be and you need to replace it.

Just from appearances my serpentine may last the life of the engine, it’s not being bent backwards like they normally are with an tensioner pulley, and so far I can detect no wear.

[Ostinato]

Originally Posted by Training Wheels

Funny, I just ordered a serpentine belt conversion for my 70A alternator. Got tired of the belt dust.

Training Wheels- Where did you get the kit. I am well past being tired of the dust

[rgleason]

Why would a serpentine belt be more efficient? If it is due to tension etc., not sure it’s a big difference.

Good question. I'll hazard a guess. The V depends on tension and friction from driving the belt down into the V, the same forces have to be removed for the belt to become free, thus there is an additional load on the engine.

If a V and a serpentine belt were tensioned on two freely spinning pulleys, which one would be easier to spin? It can't be too much of a difference, but I am pretty sure there is one.


I have a question actually 2.

Is there any belt dust with serpentine?
Is it quieter?

[a64pilot]

Originally Posted by Ostinato

Training Wheels- Where did you get the kit. I am well past being tired of the dust

I think Balmar bought someone out and most are Balmar Alt Mount Kit’s.
Google for best price, although we do have at least one sponsoring vendor here that sells them, maybe more.
Electromaax also sells a kit, that is I believe lower price than Balmar’s.
However there have been many reports of people not being happy with their after the sales and warranty service, where I don’t think I have ever heard of an issue with Balmar.

Kit is a two beer job on my engine, changing the alternator pulley was the hardest part, installing on the engine is easy.
You may want to transfer the TDC Mark from your factory crank pulley to the serpentine pulley, the serpentine pulley just overlays the factory one as it is also usually a harmonic balancer, but mine covered the TDC mark.
Real easy install. I also got a spare belt, but it looks like it may never be needed.

[Training Wheels]

Originally Posted by Ostinato

Training Wheels- Where did you get the kit. I am well past being tired of the dust

PKYS. Very knowledgeable.

[a64pilot]

Originally Posted by rgleason

Good question. I'll hazard a guess. The V depends on tension and friction from driving the belt down into the V, the same forces have to be removed for the belt to become free, thus there is an additional load on the engine.

If a V and a serpentine belt were tensioned on two freely spinning pulleys, which one would be easier to spin? It can't be too much of a difference, but I am pretty sure there is one.


I have a question actually 2.

Is there any belt dust with serpentine?
Is it quieter?

Zero belt dust.
Serpentine belt squeaks a little for the first minute after I start, then is quiet. I have no idea why, I have not put belt dressing or anything on it cause it’s not an issue, just don’t know why it squeaks for a minute, not a loud squeak.
Perhaps I don’t have it tight enough, I run it about like you run a normal car belt, 1/2 “ of movement when pushed by your thumb with just a little pressure, but it does not slip. I figure real tight is bad on bearings.

[Jammer]

Originally Posted by rgleason

Serpentine belt advantages:

The advantage of multi-V belts is that they offer a larger contact area for a given pulley diameter without requiring multiple belts. Every other benefit comes from that.


The "serpentine" feature, where the belt is routed in such a way that the back of the belt is used to drive certain accessories in a reverse direction, is used in automotive applications, but is not ordinarily used in alternator conversions on marine engines.

1. drives larger alternators easily

Can also do with multiple belts. In some cases, there are kits available.

1. more efficient power transfer, less energy loss to belt.
2. uses less energy, more efficient, requires less HP
3. less belt tension required, better for bearings on engine and alt
4. belt tension is not as big an issue as V.
5. less slippage, less heat
6. less dust
7. quieter

V belts behave badly when overloaded and when run on pulleys that are too small. All the things you list are symptoms of an overloaded belt that has been overtensioned to make it work.


Now, switching from a V belt to a serpentine belt is certainly one way to fix that, and there are kits available, and it's a solution that fits the space easily. That doesn't mean that it is the only possible solution, or the best one for cruising.


The main drawback of multi-v belts is that replacement parts availability is comparatively poor. Compounding this, the alternatives for a temporary repair are also poor. In contrast, you can get v-belts everywhere, and can get by with a v-belt that isn't an exact match, at least for a while.


I would prefer a 2-V or 3-V setup over a serpentine setup, for cruising, for these reasons.


Using undersize alternator pulleys to improve output at idle makes matters worse. A large frame alternator, that will perform better at low speeds, will put fewer demands on the belt drive system overall.

[phantomracer]

installed the alt-belt kit from Balmar on my yanmar 3gm-30 w/100amp balmar alternator

The alternator WAS eating belts.. engine bay was all black from dust.

The serpentine belt made a huge difference. Still a hair of dust, but not a dust storm like before. Afraid of making the belt too tight and damaging something.

[rgleason]

All the things you list are symptoms of an overloaded belt that has been overtensioned to make it work.

I have a small case 90-65 amp Balmar from 1995, I don't have the belt tightened too much (1/4" as instructed) and I get belt dust on this new, becoming old, engine.


Very Good point about availability, but they send you two belts and a64pilot says he doesn't think he'll be using the second one.


Just to be a bit argumentative, both belt types have friction, however I believe the V has more. Don't know if it is worthwhile trying to measure it, but the design of the V is intended to clamp the belt creating friction. Maybe the newer belt is a response to some of the V belt issues? -I know nothing about belts really, except my Dad was an inventor and was always building stuff. One of his favorite things was a stick of "belt grease". He would get his machines going and then apply the stick to the back of the belt that was slipping. It was a little dangerous but worked like a charm. Maybe that's what we all need so we can have a looser belt that does not dust..


I guess these belts aren't really noticeably quieter.


Thanks for all the good feedback. Did any of you making the change to serpentine have to change your system coolant pipes? I saw a note about possibly having to change the lower coolant pipe on a 3ym30 (on PKYS site). Can anyone who has 3YM30 and serpentine, confirm this or advise otherwise?

[john61ct]

Serpentine means no worries if your **continuous output** is 60-70A or above.

There are so many vee belt configurations, I'm sure between there and 100A, some of them don't produce much dust.

But if you need to upgrade, why not go to the certain solution?

[txg]

Our Mitsubishi/Vetus engine came with a stock 110A alternator and a single v-belt.



At cruising RPM it produces a continuous output of about 90-100amps. There is not much belt dust or wear. Recently i changed the belt for the first time just to be on the safe side. The old belt still looked okay so i kept it as an emergency spare. The old belt was used for more than 700 hours.



So there is no reason to switch to serpentine for us...

[deluxe68]

Originally Posted by a64pilot

I’d say 80 from just my experience is the absolute max on a single belt and only then if you don’t mind excessive tension and alignment is spot on perfect.
Why would a serpentine belt be more efficient? If it is due to tension etc., not sure it’s a big difference. For me the deciding factor was the excess tension and belt dust from a single belt.
My stock 80 would start dusting as soon as tension even approached correct, and I assume once the belt starts throwing dust, it’s worn slick and is thinner than it should be and you need to replace it.

Just from appearances my serpentine may last the life of the engine, it’s not being bent backwards like they normally are with an tensioner pulley, and so far I can detect no wear.

Heat builds up on a v-belt partly because of how much it has to bend around the small pulleys. The fact that they are much thicker than serpentine belts means there is more stress on them. Heat is a big killer of small v-belts.

The other killer is abrasion from corroded steel pulleys. The serpentine kit I have from Balmar is aluminum so it should not wear down the belt.

[deluxe68]

Originally Posted by phantomracer

installed the alt-belt kit from Balmar on my yanmar 3gm-30 w/100amp balmar alternator

The alternator WAS eating belts.. engine bay was all black from dust.

The serpentine belt made a huge difference. Still a hair of dust, but not a dust storm like before. Afraid of making the belt too tight and damaging something.

When we opted for the AT-165 alternator we also put the belt kit on our 4JH2E, the spacing was about 1/2” off on the water pump. I had to pay the boatyard to fabricate a spacer to get it lined up correctly. When I contacted Balmar they could not care less that their product did not fit correctly.