Serpentine vs dual V belt?

[reflectionsv37]

I converted my Yanmar 3JH3E to a serpentine belt 8 years ago when I upgraded to a 160amp alternator. The kit was a perfect fit from Elecromaax. I was replacing the single belt with a 110amp balmar twice a year. I haven't had to replace a belt since I upgraded. Highly recommend the serpentine!

[Coltrek]

I converted to Serpentine this spring, was a little pricy, but I just wanted to get away from V Belts, Period. For the 12V alternator, I used the kit from Balmar, they are machined perfectly, the only thing I didn't like is the narrow V, I think 12V's . The other two belts are K8, like a car or light truck. They work swimmingly. Yanmar 4JH3-HTE.

[SV-Viento]

We made the conversion from a V to Flat/serpentine belt on a Yan 3YM30 (Using a Balmar Kit) and was hands down one of the best improvements we made to the boat. It eliminated belt dust and ware, decreased/removed Alternator slippage when the alternator is under load, and decreased engine vibration/noise. All common problems with the 3YM30. I love this engine and belt combo. Reliable and super quiet.

[Highlander40]

poly-V belts are great as long as the pulleys are all in the same plane. I had a retrofit on Yanmar 6LY STE engines and the belts self destructed and finally flew off. Hinckley did the swap as a test. They gave up on fitting older engines with poly-V belts

[sdj]

If you are using it offshore, the vee belts will be far easier to source should you have a mishap.

If you do go to poly-vee belts, consider adding an overrun clutch to the alternator for torsional vibration purposes.

[NYSail]

Originally Posted by sdj

If you are using it offshore, the vee belts will be far easier to source should you have a mishap.

If you do go to poly-vee belts, consider adding an overrun clutch to the alternator for torsional vibration purposes.

I do agree about sourcing, however If I'm going off shore I will have half a dozen belts. As it is I always have 2 spares on board.....

[IOM]

The serpentine belt is usually a better choice of belt, (remember it is 5 to 8 V belts in parallel) however they do suffer a bit because of less space to wear down, because the V is so small. As soon as the crest of the V on pulley touches the root of the V on the Belt they no longer grip on the pulley very well , because they no longer ride on the V but on the crest of the tooth on the pulley.
One other thing to consider, is where you will go cruising. I am not so sure serpentine belts will be as widely available as V belts, but that's another discussion.


Fitting an auto (spring and damper) adjuster just wont work on any of the marine alternators I have seen pictures of. The reason is simple and is caused by the very nature of diesel engines. A diesel engine , by virtue of its high compression, followed by high energy power stroke, will never rotate at a constant velocity. This is a huge problem at idle, and with increased rpm does diminish somewhat. (this is one of the reasons for the ridiculous sized flywheel mass on a diesel engine is to try minimize this)
A rotating mass of copper and Iron will want to rotate at a constant velocity, and so you continually have a conflict between the engine rpm variation and the constant alternator rpm. This creates terrific backlash on the belt, resulting in the belt "flapping" a lot , unless its run extremely tight (which the spring and damper arrangement does not do)


Adding a bendix drive (one way drive with free over run ) to the alternator , removes this conflict in drive speed problem, and the spring tensioner works very well then. It is also less abusive on the belt, and all but removes the "flapping " of the belt
This is very common on automotive diesel alternators.


Any device with a large rotational mass driven by a diesel engine at low rpm needs a bendix drive (one way drive) in order to extend the life of the drive belt. Camshafts, water pumps etc all have a very low rotational mass, and so never overload the belts.

[a64pilot]

Well, Diesel engine cars and trucks run serpentines with spring tensioners and have done so for decades. They are often driving power steering pumps and airconditioner compressors on the same belt too.

[MJWEENZ]

Is anyone aware of a serpentine belt kit for the Ford Lehman SP135? I know there is one by Balmar for the 120 but no one can tell me if it will work on the 135.

Mike

[sailingharry]

Originally Posted by rom

I converted my two 4JH4E to serpentine last winter. I did not buy the expensive balmar kit but simply purchased the serpentine parts from Yanmar (4JH5 I think, compatible with 4JH4, may not be compatible with yours) for less than 150EUR. It is 6V belt though, not 8V. It is driving a 200A delco 28SI, no problem so far.


I think the genuine yanmar system is superior to the above picture as it comes with an additional pulley that pushes the belt up to the alt and provides more contact between alt pulley and belt. Also allowed me to use a longer belt and move the alt far away from the engine.

I've done some Googling, and been unsuccessful. So, I have to ask. Do you a have a source, a part number, or any other lead on this Yanmar kit? I'm VERY interested! I have a 4JH2E, which I assume will match.



Harry

[sailingharry]

Originally Posted by sailingharry

I've done some Googling, and been unsuccessful. So, I have to ask. Do you a have a source, a part number, or any other lead on this Yanmar kit? I'm VERY interested! I have a 4JH2E, which I assume will match.



Harry

OK, for those that are reading this, I answered my own question. I assume the alternator pulley is standard. This leaves the rest. The crank pulley on the 4JH2E has 4 bolts, the 4JH5E has 3, so that V-pulley has to be replaced too. Here are the parts:


Fresh Water Pulley

129271-42350 PULLEY,CW PUMP 6PK



Crank Pulley (the 4JH2E has a 4-bolt pulley, so I need both parts).

119802-21660 V-PULLEY, 120
129271-21660 PULLEY, CRANK 6PK


Serpentine Belt
129271-77680 BELT,ALTERNATOR


Idler Pulley

129271-77651 BOLT,IDLER BELT
129271-77660 IDLER ASSY,BELT 25.5


I'm working up a price now.

[tdgaffney]

Originally Posted by SV-Viento

We made the conversion from a V to Flat/serpentine belt on a Yan 3YM30 (Using a Balmar Kit) and was hands down one of the best improvements we made to the boat. It eliminated belt dust and ware, decreased/removed Alternator slippage when the alternator is under load, and decreased engine vibration/noise. All common problems with the 3YM30. I love this engine and belt combo. Reliable and super quiet.

I'm thinking of changing my 3YM20 V-Belt to a serpentine and upgrading the alternator from 80 amps to 120 amps. The 3YM20 is very much like the 3YM30 - could you tell me the Balmar Kit part number you purchased?


Thanks, tom