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Old 11-10-2019, 19:53   #1
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Balmar Alt-Belt Tension

Loving the Alt-belt on my Yanmar 3GM30f

The system is (circa 1992) 100 amp Alternator, 614 regulator.

Earlier this year, noticed a bad bearing noise in the alternator, had it rebuilt. it was also masking a squeak noise, like a slipping belt.

Unscientifically, and not wanting to make the belt tension too tight, set the tension just tight enough that, turning the fan of the alternator by hand, til there was no slippage, and there was slight movement of the other 2 pulleys. This left about a 3/8 to 1/2" deflection between the crank and the water pump.

Looking at the manual (I know.....what a concept) noticed it said it should be 1/32" deflection. That would make how I tensioned it WAY too loose!

question... Is the recommended 1/32" deflection accurate? Just worried about bearing issues down the line. My monkey brain just thinks that is way too tight. Should I just not wimp out and tighten it more?
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Old 11-10-2019, 22:05   #2
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Re: Balmar Alt-Belt Tension

I am in the process of upgrading to a 100-amp Balmar alternator and had the manual open when I saw your post. It says the following:

Typically, belt deflection should be between 1/4” and 3/8” when you push your thumb down on the back of the belt at mid-span between pulleys. For more precise tensioning adjustment, use a commonly available tensioning gauge. The use of a belt tensioner, or pulley jack, makes it easier to adjust the belt tension by using mechanical means to push the crank pulley and the alternator pulley apart. One such device, sold by MSC Industrial Supply 1-800-645-7270 (Part. # 35438209) is designed to provide “hands-free” tensioning for V-Belts.
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Old 11-10-2019, 22:20   #3
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Re: Balmar Alt-Belt Tension

Quote:
Originally Posted by gamayun View Post
I am in the process of upgrading to a 100-amp Balmar alternator and had the manual open when I saw your post. It says the following:

Typically, belt deflection should be between 1/4” and 3/8”
For which engine? The manuals are different for each engine.

for my Yanmar 3GM30f, the manual is here http://www.balmar.net/wp-content/upl...-YSP-3GM-B.pdf

On page 4:
Quote:
10-groove, J-type belt, that deflection is 1/32" per one inch of belt span between pulleys under 25 pounds of deflection pressure.
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Old 11-10-2019, 22:26   #4
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Re: Balmar Alt-Belt Tension

OK ...I see it now.. after reading what I pasted.. see it is 1/32 per inch of belt span!

Doing some mental math, Looks like 1/4 to 3/8 will be just about right.. probably need to tighten the tension just a wee bit more. I do have their Belt Buddy installed, which makes minor adjustments very easy!

So good thing I didn't actually do 1/32 total.

I guess reading the entire sentence is helpful, not just look for the number!
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Old 11-10-2019, 22:38   #5
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Re: Balmar Alt-Belt Tension

I have been having a similar problem getting, and keeping, the right tension on my alternator belt. Mine is 110 amp alternator with a half inch V belt. From what I have read, this size of alternator is the upper limit for a V belt and it probably should be a serpentine belt. However I have no room to fit a serpentine pulley so I am stuck trying to get sufficient tension on the belt.

I first took mine into a marine electrical shop and had them confirm that the belt I was using was the correct size, material and profile for the pulleys.



To check that there is enough tension they recommended starting the engine from cold, running it for five minutes and then checking how hot the pulley on the alternator is. If it is hotter than the alternator body, then the belt is slipping and needs to be tightened. The alternator pulley is smaller than the one on the engine so any slippage will be on the alternator pulley. So, according to the electrical shop, keep tightening the belt until the alternator pulley is runing no hotter than the rest of the alternator.



Hope that helps.
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Old 11-10-2019, 22:41   #6
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Re: Balmar Alt-Belt Tension

Not making excuses for myself for being retarded.. but the 1/32 was at the end of the line.. i didn't read the next line/rest of the sentence .. in my head I had the answer after seeing 1/32, so I just stopped reading

Quote:
Once the belt is around all three pulleys, the alternator can be moved away from the engine
block to add tension to the belt. The recommended tension for the serpentine belt can be
measured by the deflection over a given span. In a 10-groove, J-type belt, that deflection is 1/32"
per one inch of belt span between pulleys under 25 pounds of deflection pressure.
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Old 11-10-2019, 22:50   #7
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Re: Balmar Alt-Belt Tension

Quote:
Originally Posted by osprey877 View Post
I have been having a similar problem getting, and keeping, the right tension on my alternator belt. Mine is 110 amp alternator with a half inch V belt. From what I have read, this size of alternator is the upper limit for a V belt and it probably should be a serpentine belt. However I have no room to fit a serpentine pulley so I am stuck trying to get sufficient tension on the belt.

I first took mine into a marine electrical shop and had them confirm that the belt I was using was the correct size, material and profile for the pulleys.



To check that there is enough tension they recommended starting the engine from cold, running it for five minutes and then checking how hot the pulley on the alternator is. If it is hotter than the alternator body, then the belt is slipping and needs to be tightened. The alternator pulley is smaller than the one on the engine so any slippage will be on the alternator pulley. So, according to the electrical shop, keep tightening the belt until the alternator pulley is runing no hotter than the rest of the alternator.



Hope that helps.
Thats the reason I went with the Alt Belt kit. Just couldn't keep the V belt from dusting, even with the tension very high, with very little deflection (likely too much). Now there is zero dusting with the 10 rib belt. I too have less than an inch clearance around the pulley, but it does fit just fine.. just barely

If the al-belt kit is not an option, I would at least get the Belt Buddy. You can adjust the tension in virtual micrometers at a time, and lock it in...and make adjustments later on if needed.

Not getting any dusting now, but was thinking there might be some minor slippage as I have it at about 1/2" or so deflection by hand, without the alternator drag when it is working.

I was just concerned about seeing 1/32" deflection in the manual.. but as i just pointed out, that is per-inch of pulley length, not total!
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Old 11-10-2019, 22:59   #8
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Re: Balmar Alt-Belt Tension

Some good info here on belts and squealing sounds. Now this makes me want to check whether I have a 1/2" or 3/8" pulley....

https://marinehowto.com/marine-alter...n-tips-tricks/
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Old 11-10-2019, 23:19   #9
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Re: Balmar Alt-Belt Tension

Quote:
Originally Posted by gamayun View Post
Some good info here on belts and squealing sounds. Now this makes me want to check whether I have a 1/2" or 3/8" pulley....

https://marinehowto.com/marine-alter...n-tips-tricks/
Yup a great article by Rod.....like the rest of his writeups..great information!

I keep meaning to check the alignment of the pulleys..hope I remember to do it this winter during lay up...visually, it is dead on balls..but i really should get a straight edge across the pulleys to ensure it is straight
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