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06-07-2016, 11:40
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#31
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Registered User
Join Date: Apr 2011
Location: NZ
Boat: S34 Bob Stewart - 1959 Patiki class. Re--built by me & good mate.
Posts: 1,062
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Re: Alternator Belt issue 3YM30
Quote:
Originally Posted by puffcard
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
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At 60% efficiency for V belt system (if you are lucky) 2.25/0.6 =3.75hp
Rule of thumb, IIRC, is 20-25A /hp = 4+
Definitely will give Dayco belts a try.
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06-07-2016, 11:51
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#32
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Registered User
Join Date: Apr 2013
Location: Manly, Qld, Aust
Boat: Fusion 40
Posts: 174
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Re: Alternator Belt issue 3YM30
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.[/QUOTE]
Belt dust everywhere which makes for untidy engine bay.
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06-07-2016, 12:12
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#33
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Registered User
Join Date: Apr 2011
Location: NZ
Boat: S34 Bob Stewart - 1959 Patiki class. Re--built by me & good mate.
Posts: 1,062
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Re: Alternator Belt issue 3YM30
Quote:
Originally Posted by jacktheflyer
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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Belt dust everywhere which makes for untidy engine bay.[/QUOTE]
+1
I didn't consider how much would go into the air filter.
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06-07-2016, 16:45
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#34
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Registered User
Join Date: Dec 2015
Posts: 7
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Re: Alternator Belt issue 3YM30
Most alternator belts wear out because of either alignment or slippage. Getting a serpentine belt is step one to handle the load. {I also like Gates Green Stripe} If you see belt dust and/or hear a bit of a squeal at starting, simply spray water on the belt. If the sound goes away, alignment is off. If it gets worse, belt tension is off. Don't use the 'finger depression test." Get a tension meter. Cheap and effective. Also, many 120+ amp alternators require two belts and pulleys to work efficiently.
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06-07-2016, 21:06
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#35
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Registered User
Join Date: Sep 2011
Location: Western Australia
Boat: Schionning Wilderness 1320
Posts: 18
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Re: Alternator Belt issue 3YM30
I got one electromaax serpentine kit to test out on our Portside 3YM30 a year or so ago. Beautiful gear.
But alas, once all installed, the pulley for the alternator was 5mm further out than the crank pulley and water pump pulley. The alternator has no movement fore/aft so I couldn't get good alignment. (3.15" saddle mount) Their suggestion when emailed was to purchase one of their alternators or machine the pulley down. I didn't actually need a larger output alt, was just tying to reduce belt dust.
I thought that I had read on their website recently that they now have two different pulleys but I can't find it again. Anyway, after numerous emails with no reply, I gave up and reinstalled the original pulleys.
I'm sure the serpentine belt would help stop belt wear but with the stock 80A hitachi, you would have to muck around a bit to get all pulleys aligned. (Unless the design has changed)
I see that the new 3YM30AE now has serpentine belt and larger alternator
So if going down the electromaax serpentine belt road for a 3YM30 and keeping the stock alternator, get confirmation that it now fits.
Sent from my iPhone using Cruisers Sailing Forum
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06-07-2016, 21:23
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#36
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Registered User
Join Date: Aug 2011
Location: Victoria, BC
Boat: Catalina 36 MKII
Posts: 1,104
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Re: Alternator Belt issue 3YM30
Quote:
Originally Posted by Sberg
I see that the new 3YM30AE now has serpentine belt and larger alternator
So if going down the electromaax serpentine belt road for a 3YM30 and keeping the stock alternator, get confirmation that it now fits.
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.... and take whatever electromaax tells you with several pounds of salt ....
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07-07-2016, 10:06
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#37
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Registered User
Join Date: Jun 2010
Boat: Gemini 105Mc+
Posts: 865
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Re: Alternator Belt issue 3YM30
I too have had abnormal belt wear on both my 2GM w Haitachi 55A.
I found that the holes in the alternator with 10 mm dia while the hole in the engine casting was less than 9 mm and the bolt about 9 mm. So I ordered 10 mm bolts, carefully drilled out the casting and put on a new YM belt. After about 12 hour, it needed tightening. Then 14 hours later, I notice the top of the belt was below the pulley and needed tightening again. The alignment "looks" OK ( will check with a longer straightedge this WE). Based on this, I am expecting only about 75 - 100 hours out of the stock belt...seems way too short. it cannot be the alternator load as I have plenty of solar and with both engines running, the load has to be small. Is heat a factor?
Ed
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07-07-2016, 11:06
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#38
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Moderator Emeritus

Join Date: Oct 2013
Location: Jacksonville/ out cruising
Boat: Island Packet 38
Posts: 31,351
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Re: Alternator Belt issue 3YM30
Quote:
Originally Posted by Jd1
.... and take whatever electromaax tells you with several pounds of salt ....
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I would personally be very hesitant to purchase anything from them based on numerous reports I have seen.
We have a Vendor or two here that will sell you the Balmar kit.
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16-03-2017, 23:44
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#39
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Registered User
Join Date: Apr 2013
Location: Manly, Qld, Aust
Boat: Fusion 40
Posts: 174
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Re: Alternator Belt issue 3YM30
Quote:
Originally Posted by Sberg
I got one electromaax serpentine kit to test out on our Portside 3YM30 a year or so ago. Beautiful gear.
But alas, once all installed, the pulley for the alternator was 5mm further out than the crank pulley and water pump pulley. The alternator has no movement fore/aft so I couldn't get good alignment. (3.15" saddle mount) Their suggestion when emailed was to purchase one of their alternators or machine the pulley down. I didn't actually need a larger output alt, was just tying to reduce belt dust.
I thought that I had read on their website recently that they now have two different pulleys but I can't find it again. Anyway, after numerous emails with no reply, I gave up and reinstalled the original pulleys.
I'm sure the serpentine belt would help stop belt wear but with the stock 80A hitachi, you would have to muck around a bit to get all pulleys aligned. (Unless the design has changed)
I see that the new 3YM30AE now has serpentine belt and larger alternator
So if going down the electromaax serpentine belt road for a 3YM30 and keeping the stock alternator, get confirmation that it now fits.
Sent from my iPhone using Cruisers Sailing Forum
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Do you still have the kit you removed?
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17-03-2017, 02:52
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#40
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Registered User
Join Date: Sep 2011
Location: Western Australia
Boat: Schionning Wilderness 1320
Posts: 18
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Re: Alternator Belt issue 3YM30
'Do you still have the kit you removed?'
JackTheflyer,
It's a long story but it is being returned.
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09-12-2019, 15:50
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#41
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Registered User
Join Date: Feb 2018
Posts: 10
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Re: Alternator Belt issue 3YM30
I have the new Yanmar 3YM AE which features a serpentine toothed belt. Can anyone tell me if there is an equivalent belt to the factory Yanmar belt , available at a more reasonable price
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10-03-2022, 05:50
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#42
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Registered User
Join Date: Jan 2019
Posts: 2
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Re: Alternator Belt issue 3YM30
What belts seem better than the Yanmar belts? Hold up better,etc? 37.5” is Yanmar belt length and it is smooth. Smooth or clogged?
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10-03-2022, 11:45
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#43
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Registered User
Join Date: Apr 2011
Location: NZ
Boat: S34 Bob Stewart - 1959 Patiki class. Re--built by me & good mate.
Posts: 1,062
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Re: Alternator Belt issue 3YM30
Gates green stripe segmented 100+ hr 100A.
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