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Old 05-07-2016, 15:52   #16
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Re: Alternator Belt issue 3YM30

How are you tensioning the belts ?
There is a chance you are not adjusting then properly.
I've seen many cases where the owners just don't tighten them enough and that caused slipping.

Check the specs on your engine for tensioning instructions. You may discover that they recommend a tighter belt then you are making it.
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Old 05-07-2016, 16:11   #17
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Re: Alternator Belt issue 3YM30

Quote:
Originally Posted by Stu Jackson View Post
Y

PS - I DO run a 100A alternator on a 3/8" belt.
Ya made my day. I DO have a chance of success.

I just sent a scathing email to DB electrical for sending me an 120A alternator with a three eights inch pulley.

My ratio is 148:98 approx 1.5:1 giving me 3300 @2200rpm. (110A,cold. I guess)
Yea I know too slow. Coke up the old girl. I give it a blast every now and then. 2200 is nice on the ears.
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Old 05-07-2016, 16:37   #18
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Re: Alternator Belt issue 3YM30

The pulley size will not change the output of the alternator. People who are having problems with alternator output or charging at engine idle, maybe a smaller pulley is all you need. By reducing the pulley size your alternator will start producing power sooner and produce more power at lower RPMs. Also, because your alternator is spinning faster the fan will move more cooling air through the alternator adding to component life, to little air flow can burn up an alternator. Using a larger alternator pulley you'll need more RPMs to get the output and get less airflow. 100 amp alternator at cruising speed is going to put out 100 amps if the charging system is asking for it, with either a large or small pulley. The regulator is the only way.

I ran a 110 amp alternator with a v-belt for several years. I've dialed it back to 90 and plan to go to 80 this fall, cause we'll be motoring most days down the ditch.
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Old 05-07-2016, 18:03   #19
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Re: Alternator Belt issue 3YM30

I had the same problem and currently use gates green stripe belts which helps but is certainly not an answer the serpentine belts is an answer but the kit is expensive and requires good access to the front of the engine or pulling them. I get 80 to 100 hrs out of my belts
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Old 06-07-2016, 03:14   #20
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Re: Alternator Belt issue 3YM30

Quote:
Originally Posted by puffcard View Post
The pulley size will not change the output of the alternator.
Not correct. For a given engine RPM a larger pulley lowers the alternator rpm putting out less amperage.
Just look at the performance curve of any alternator.

I do agree that external regulation with the ability to control field strength is the best way to set output.
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Old 06-07-2016, 04:58   #21
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Re: Alternator Belt issue 3YM30

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Originally Posted by Bob the builder View Post
Hi scrubby I have same boat same motors and same problem and have tried various remedies rust on the pulleys contributes to belt wear an old auto elec. told me,pretty hard to stop it .am looking into serpentine belts. Will let you know results
Bob
The serpentine belt looks (to me) to be the best option but is also the most expensive.
Scrubby
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Old 06-07-2016, 05:01   #22
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Re: Alternator Belt issue 3YM30

Quote:
Originally Posted by twinboat View Post
How are you tensioning the belts ?
There is a chance you are not adjusting then properly.
I've seen many cases where the owners just don't tighten them enough and that caused slipping.

Check the specs on your engine for tensioning instructions. You may discover that they recommend a tighter belt then you are making it.
Twin boat
I make them as tight as I can and retighten after the first run on new belts. I would say that I am overtightening the belts which potentially will cause premature failure in the bearings.
Scrubby
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Old 06-07-2016, 05:02   #23
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Re: Alternator Belt issue 3YM30

Quote:
Originally Posted by twinboat View Post
How are you tensioning the belts ?
There is a chance you are not adjusting then properly.
I've seen many cases where the owners just don't tighten them enough and that caused slipping.

Check the specs on your engine for tensioning instructions. You may discover that they recommend a tighter belt then you are making it.
Twin boat
I make them as tight as I can and retighten after the first run on new belts. I would say that I am overtightening the belts which potentially will cause premature failure in the bearings.
Scrubby
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Old 06-07-2016, 05:05   #24
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Re: Alternator Belt issue 3YM30

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Originally Posted by DeepFrz View Post
One other possibility is that the belts you are using are not the same angle as one or both of the pulleys. Possibly the alternator pulley is not a match for the flywheel pulley angle wise or is to small and puts undue load on the belt by bending sharply or the pulleys are not in exact alignment. Are the belts 1/2 in. or 3/8 in.?
Tks DeepFrz

Pulley alignment is good.

Scrubby
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Old 06-07-2016, 05:11   #25
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Re: Alternator Belt issue 3YM30

From quick start:
Alternator pulley belt wrap, what does that mean? Belt wrap is the contact area the belt has with the pulley. but the greater the belt wrap the longer belt and pulley life can be expected. Alternators take quite a bit of power to run so good belt contact with the pulley is very important. If you have poor belt wrap or your pulley becomes "glazed" a glazed pulley looks very smooth it may be time to replace the pulley.
https://alternatorparts.com/alternator-pulley-size.html

Well it better work for the interim, 'cos that what I am doing on my diminished budget. I think alignment, pulley surface condition & correct tension play a decent part as well.

I may externally regulate as well, but not with a fancy $400
USB ---> PC unit, rather a ZM4, with a pot. $175US
alternator, smart alternator regulator

Probably put a couple of temp alarms in at $10 each. ( Eventually)[/QUOTE]

This getting to the crux of the issue.
-Unfortunately don't have external regulation or I would try this
-The pulleys are definately glazed and highly polished form the amount of belts that have been worn out (but the pulleys are still dimensionally adequate)
-If I could work out how to automatically tension the belt would help the belt wrap

Scrubby
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Old 06-07-2016, 05:18   #26
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Re: Alternator Belt issue 3YM30

Quote:
Originally Posted by DeepFrz View Post
One other possibility is that the belts you are using are not the same angle as one or both of the pulleys. Possibly the alternator pulley is not a match for the flywheel pulley angle wise or is to small and puts undue load on the belt by bending sharply or the pulleys are not in exact alignment. Are the belts 1/2 in. or 3/8 in.?
I don't remember what sectional size they are but to my knowledge all small belts are 40 deg angle and they do fit the pulleys being slightly proud when new

Scrubby
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Old 06-07-2016, 05:32   #27
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Re: Alternator Belt issue 3YM30

Belt tension should only be tight enough so you can not move the alternator by pushing on the fins.

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Old 06-07-2016, 05:34   #28
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Re: Alternator Belt issue 3YM30

Belt tension should only be as tight so you can not force the alternator to move by turning the cooling blades. Any tighter and you will burn bearings .

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Old 06-07-2016, 07:21   #29
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Re: Alternator Belt issue 3YM30

Quote:
Originally Posted by SimonV View Post
Belt tension should only be as tight so you can not force the alternator to move by turning the cooling blades. Any tighter and you will burn bearings .

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That might be ok for a car or low output alternator, but not 120amp setup.

A changing system putting out 120amps requires 2.25hp, thats a good load. The raw water pumps which only need about 1/8hp can run much looser.

745watts = 1Hp
14V x 120amps = 1,680 watts
1,680 watts/745 = 2.25HP

Mainesail likes the E-Maax belt conversion, not cheap but very quality as expected.
High Output Alternator Serpentine Pulley Kit Install | SailboatOwners.com Forums

Also by the chart you can see there is less than 10% change in output between 1500 RPM and 6000 RPM. The output curve flattens out.
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Old 06-07-2016, 08:10   #30
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Re: Alternator Belt issue 3YM30

After fighting belts for a year, I gave up and went Serpentine, the Balmar one which I believe they buy from someone else?
Anyway belt life seems like will be in the thousands of hours now even though I now have a 125 amp Alternator.
If you have the option to change the belt ratio, you want to speed up the alternator, as it is, they are not spun nearly fast enough for cooling and longevity, once you go serpentine and solve the belt issue, your next limiting factor will be alternator cooling that will either limit the output if your temp protected, or burn up your alternator if your not.

Have to ask, where does the belt dust go? I can tell you where a lot of mine went, into the engine is where. The factory Yanmar "air filter" isn't much for filtering, assumption is I'm sure that boats don't operate in dusty environments, but if your making belt dust, most likely your engine is eating a lot of it.
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