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Thread: Alternator Belt Woes

  1. #1
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    Default Alternator Belt Woes

    The alternator belt on the boat needed replacing. I like to have two spares and only had one, a cheaper brand. so I bought two v belts from NAPA; they weren't cheap. I put one on the engine and all was well yesterday for about 4 hours of running. This morning, there was terrible squeal when I started the engine. I tightened the belt and the squeal was still there. So I put on the cheaper belt. No squeal and it worked as it should for almost five hours.

    Any thoughts? Did I get a defective belt from NAPA?
    Elect a clown expect a circus

  2. #2
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    Default Re: Alternator Belt Woes

    I never run anything but the green belts from Gates & NAPA (theirs are made by Gates). They will have to be adjusted at least once, maybe twice, but then they just last & last.

    Are you sure some liquid or oil didn't get on your belt? Even a couple of drops can make a belt squeal.
    "If it ain't broke, you're not trying." - Red Green

  3. #3
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    Default Re: Alternator Belt Woes

    thanks for the tip. Not sure how I would get some liquid or oil on the belt overnight when I didn't touch it
    Elect a clown expect a circus

  4. #4
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    Default Re: Alternator Belt Woes

    For sure it could be a bad belt. I'd take a look to see if the water pump, valve cover, or some such, is leaking.
    "If it ain't broke, you're not trying." - Red Green

  5. #5
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    Default Re: Alternator Belt Woes

    Sure that the new belt fits the shape of the pulleys?
    I had a devil of a time getting belts for my wee M20. The green belts were too big in "cutaway" shape, (i forget the word).
    Polished up the inside surface of the pulleys? rust, dirt, glazing...

  6. #6
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    Default Re: Alternator Belt Woes

    Are your pulleys still in alignment - there is a current 'thread' over on the Moyer Marine Forum (no affiliation) discussing this situation -- www.Moyermarineforum.com




    Rick

  7. #7
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    Default Re: Alternator Belt Woes

    Quote Originally Posted by wizbang 13 View Post
    (i forget the word)
    Cross-section mebbe?

    Quote Originally Posted by hawkeye54 View Post
    Are your pulleys still in alignment…?


    I had the same thought when reading the OP this morning. Misaligned pulleys continue to be the death of many an otherwise good V-belt.

  8. #8
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    Default Re: Alternator Belt Woes

    if it's misalignment, why doesn't the cheap belt squeal?
    "If it ain't broke, you're not trying." - Red Green

  9. #9
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    Default Re: Alternator Belt Woes

    Cheap belts are often softer, more compliant. They’ll not complain from the misalignment but will heat up faster from it and the flexing they endure going around any pulleys, not hold up over time.

  10. #10
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    Default Re: Alternator Belt Woes

    I will check the alignment
    Elect a clown expect a circus

  11. #11
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    Default Re: Alternator Belt Woes

    Quote Originally Posted by wizbang 13 View Post
    Sure that the new belt fits the shape of the pulleys?
    I had a devil of a time getting belts for my wee M20. The green belts were too big in "cutaway" shape, (i forget the word).
    Polished up the inside surface of the pulleys? rust, dirt, glazing...
    This was my first thought. Some of the sectional belt sizes are so close it can be hard to determine the correct number without having an established part number. Too big is not good. Too small is worse. Make damn sure the belt is not touching the bottom of the groove. If it is, no amount of tightening will fix it.

  12. #12
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    Default Re: Alternator Belt Woes

    I did a bit more digging and found a diagram from Volvo Penta that showed two belts at the same time for the alternator and pump. Might be why I am going through belts
    Elect a clown expect a circus

  13. #13
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    Default Re: Alternator Belt Woes

    I run the water pump & a 100 amp alternator on a single green belt. Normal belt lasts 4-5 hours, green lasts at least a season. I don't know what's so different about them, but I had a belt driven rototiller (on a garden tractor). Bought a standard V belt & it lasted about 3 hours. Green belt tilled 20+ acres over 2 seasons.

    That being said, the correct belt size & shape is crucial.
    "If it ain't broke, you're not trying." - Red Green

  14. #14
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    Default Re: Alternator Belt Woes

    green belt =kevlar bands (I think)
    big difference for sure

    Now... a solution I have resorted to in the past is to just buy the belt from the OEM dealer. They may be manufactured to spec for Volvo or Yanmar, whoever. And it may be a kevlar belt. It is not uncommon if they are built to spec. for the builder of the belt to "not compete". Which means you may not be able to buy an exact aftermarket belt from Gates or whoever made the oem part. I know that name brand belts are more expensive, but I also not that all belts are not created equally.
    Good chance your belt is metric, 3vx or similar, which is not "automotive", using different angles and widths. Just about anyone will sell you a "will fit" belt.
    How long did the original belt last?

  15. #15
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    Default Re: Alternator Belt Woes

    I got a green belt because of your suggestion. I hope it makes a difference.
    Elect a clown expect a circus

  16. #16
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    Default Re: Alternator Belt Woes

    Quote Originally Posted by Canoeyawl View Post
    green belt =kevlar bands (I think)
    big difference for sure

    Now... a solution I have resorted to in the past is to just buy the belt from the OEM dealer. They may be manufactured to spec for Volvo or Yanmar, whoever. And it may be a kevlar belt. It is not uncommon if they are built to spec. for the builder of the belt to "not compete". Which means you may not be able to buy an exact aftermarket belt from Gates or whoever made the oem part. I know that name brand belts are more expensive, but I also not that all belts are not created equally.
    Good chance your belt is metric, 3vx or similar, which is not "automotive", using different angles and widths. Just about anyone will sell you a "will fit" belt.
    How long did the original belt last?
    Kevlar? Seems to me they've been out since well before kevlar - but I could be all wrong.

    @ bobcat - hope it works for you! Be aware it will need adjustment at least once, maybe more.
    "If it ain't broke, you're not trying." - Red Green

  17. #17
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    Default Re: Alternator Belt Woes

    Kevlar is '65, adopted in tire cords by 1970.
    I'm not sure that it is "Kevlar" could be some other non stretch stuff, but that is the primary difference I think.

    If you go to the gates site and search using the filter you can note the different Vee angles, as well as width and etc
    https://www.gates.com/us/en/power-tr...00-000000.html

    This is the metric page, I see a lot of these on Japanese and German stationary engines
    https://www.gates.com/us/en/power-tr...ss-v-belt.html

    Again; if I had any doubt if it was metric or not I would by a belt from the dealer by application and "reverse engineer" it.
    (I run into this on stationary engines and the metric belts are far stronger. On 30-40 hp saws that gang up 5 or 6 belts, they won't last a day on belts from an auto parts store (We've had to resort to that in a pinch until I started stocking the correct ones) They will last a season if it is the correct belt. They all look pretty much the same on the outside !

  18. #18
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    Default Re: Alternator Belt Woes

    Thanks Jake - I learned something.
    "If it ain't broke, you're not trying." - Red Green

  19. #19
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    Default Re: Alternator Belt Woes

    A squealing (slipping) belt is the only issue? Use some “Belt dressing”. Yes, it’s a real thing. Comes in a spray can now. It puts a tacky surface on the belt and stops slipping & squealing.

  20. #20
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    Default Re: Alternator Belt Woes

    My new to me (1960s) table saw has three very short belts. I noticed that the old ones that are currently on it have stretched to slightly different lengths, so I’m guessing only one belt is doing most of the work though I haven’t noticed any problems yet. (Unless this has something to do with blade alignment Jake. ) The spec is listed in the manual as 3L 21” x 3/8”. As I understand it, the “3L” is what specs the cross section shape. So I just order three new ones.

    BTW, the 130amp alternator on my boat has two belts and they’ve been on there for almost 20 years, no noticeable problems yet. Not sure of the brand, I should check. I know they aren’t green.

  21. #21
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    Default Re: Alternator Belt Woes

    Quote Originally Posted by ron ll View Post
    My new to me (1960s) table saw has three very short belts. I noticed that the old ones that are currently on it have stretched to slightly different lengths, so I’m guessing only one belt is doing most of the work though I haven’t noticed any problems yet. (Unless this has something to do with blade alignment Jake. ) The spec is listed in the manual as 3L 21” x 3/8”. As I understand it, the “3L” is what specs the cross section shape. So I just order three new ones.

    BTW, the 130amp alternator on my boat has two belts and they’ve been on there for almost 20 years, no noticeable problems yet. Not sure of the brand, I should check. I know they aren’t green.
    Be aware that belts are sold as matched - you have to ask for matched ones though. There is enough variation in manufacturing that not all are identical.
    "If it ain't broke, you're not trying." - Red Green

  22. #22
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    Default Re: Alternator Belt Woes

    Quote Originally Posted by Garret View Post
    Be aware that belts are sold as matched - you have to ask for matched ones though. There is enough variation in manufacturing that not all are identical.
    Hmmm. Didn’t know that. These were suspiciously cheap online, maybe I’ll stop by the NAPA store today.

    Arrrgh. Labor Day so nobody is laboring and stores are closed.
    Last edited by ron ll; 09-06-2021 at 09:42 AM.

  23. #23
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    Default Re: Alternator Belt Woes

    Do NAPA and the like stock matched belts? Or is it a bigger production?

  24. #24
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    Default Re: Alternator Belt Woes

    Parts stores I worked in (back in the dark ages) usually stocked pairs of matched belts, but with most of today's cars using serpentine belts, I dunno.

    Here's more than anyone probably ever wanted to know on them (Gates - who makes NAPA belts): https://ww2.gates.com/common/printth...s&global=Gates

    Basically, there's a code on the belt that you need to match up.
    "If it ain't broke, you're not trying." - Red Green

  25. #25
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    Default Re: Alternator Belt Woes

    You might try a 3-3vx belt they will be "matched" (which is a bit of hype I think, single belts never match until they have been run in. amazon sells them, and you can return them until you sort out the proper length)

    I use a lot of this configuration belt in my work

    AFC87911-32F5-47D8-B376-1B2CC3B1B350.jpeg

  26. #26
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    Default Re: Alternator Belt Woes

    Found there was an alignment issue as many suspected. Hope it solves the problem of short belt life
    Elect a clown expect a circus

  27. #27
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    Default Re: Alternator Belt Woes

    Glad you found a reason & hope it was an easy fix.
    "If it ain't broke, you're not trying." - Red Green

  28. #28
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    Default Re: Alternator Belt Woes

    I was told they dont do matched sets of belts anymore, gates claims they are so accurate that its no longer required.... I have my doubts they are identical but i havent had issues with mine.

  29. #29
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    Default Re: Alternator Belt Woes

    I was told that, these days you have to look at the "lot number"..... all belts made from the same lot#, are are in fact, "matched"-iirc the lot number is molded/printed onto the out side of the belt, it's self.... I was working on big cooling systems at the time...I'm sure small multi belt marine applications are the same..... pretty sure it's still the way to know for sure.....hope this helps
    Last edited by the_gr8t_waldo; 10-24-2021 at 02:46 PM.

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