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NAPA belt source:

Discussion in 'Musings With Maine Sail' started by Rodd, Jan 10, 2019. Add this thread to a FAQ

  1. Rodd

    Rodd

    Joined Jan 22, 2008
    126 posts, 1 likes
    Pearson 424
    US East Hampton,NY
    After reading Maine's latest article on Alternator installation, I want to replace my aging Gates belts with the recommended NAPA Premium XL. I tried calling napa online and also went to 2 local stores, and it seems they don't make that belt in a 1/2 inch width, 45 inch circumference.
    Anyone know if this info is correct, and if so, what is the best alternative belt that will fit my requirements? Problem is you cannot look up belts by size, only by vehicle engine application, which let's most of us out!
     


  2. Ranger_12

    Ranger_12

    Joined Mar 26, 2014
    34 posts, 6 likes
    Macgregor 25
    US Kaw Lake Oklahoma
    NAPA # 25-9447 is 1/2 " X 44 7/8 should fit fine believe me I own a NAPA Store ( Napa Know How) or # 25-9447HD
     


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  3. Tom J

    Tom J

    Joined Sep 30, 2008
    1,181 posts, 144 likes
    Catalina 310
    US Quincy, MA
    Double check the V of the belt. I substituted the belt on my Universal with a NAPA belt that measured correctly, but it wore quickly and made a lot of belt dust. The V did not sit into the pulleys the way it should. I went back to the Universal belts, and no more issues.
     


  4. jssailem

    jssailem

    Joined Oct 22, 2014
    7,825 posts, 3,136 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    Read @Maine Sail file about pulley alignment. If your pulleys are not aligned you will get increased wear.

    Reading info from mechanic’s it appears Gates makes several grades of belts.

    https://www.gates.com/
     


  5. JimInPB

    JimInPB

    Joined Aug 22, 2017
    1,341 posts, 394 likes
    Hunter 212 & 170
    us West Palm Beach
    There are a few different basic universal numbering systems for V-belts here in the US. Some belts carry more than one number because that given belt meets more than one standard. Other belts just carry one number, even if they may fit another application that is specified by another standard. Some belts carry a manufacturer's stock number as well as a universal specification number.

    A half inch wide belt would be 4L in automotive nomenclature or an A series in industrial nomenclature. The numbers after that are the length. 450 would usually mean 45". If you can't get a 4L450, then you might look for an A43. If an auto parts store can't look up a belt by those numbers, then try an industrial supplier. The automotive guys may make a 44" belt & a 46" belt without making a 45" belt, but the industrial guys may fill in that gap. There are also metric measuring systems in existence. You can change to a belt of a different length by changing the diameter of the existing pulley(s) or adding an idler.

    You need to start by being sure that you have the correct width of belt. The belt should sit high in the pulley & never touch the bottom of the pulley groove. Most V-belts have a 40 degree angle, while the pulleys they ride in have around a 32 degree angle (actually 30-38 depending on the standard). The mismatch is there on purpose. The pulley grabs the belt by squeezing the sides. If the belt has worn to the point where the center of the belt touches the bottom of the pulley, then the belt is past it's service life & will not grab properly, no mater what you do. If the belt is the wrong width for the pulley, you are out of luck before you even start. 3L means 3/8" wide. 4L means 4/8" wide (4/8" = 1/2"). 5L means 5/8" wide.

    The belt length is measured on the outside circumference in the automotive measuring system. The industrial system often measures the inside diameter. The difference is usually about 2". A 450 automotive length is about the same as an industrial 43 length.

    This is a pretty good basic primer on belt measurement - https://www.regalpts.com/PowerTransmissionSolutions/Other/Belt Drive Monthly's/Form_9806E.pdf

    If your belt is making dust & slipping, then either it doesn't fit right or it isn't aligned correctly, or it is not rated for enough horsepower. If the HP rating is not enough, you can either go to duel belts, or increase the diameters of both pulleys by the same ratio & get a longer belt. You can also retrofit to a timing belt with timing belt pulleys. Those don't slip at all.

    If you want to go all the way down the rabbit hole & read up on all the specifications that apply to V-belts, then you may want to look here (assuming that you have enough time, interest & coffee) -
    https://www.baldor.com/mvc/DownloadCenter/Files/MS4050
    http://www.bearingsandindustrialsupply.com/pdf/heavy_duty_vbelt_drive.pdf

    An example of a belt with more than one numbering system listed -
    https://www.vbeltsupply.com/a43-classic-belt.html
     


    Last edited: Jan 12, 2019
    NotCook and AlexB like this.
  6. Rodd

    Rodd

    Joined Jan 22, 2008
    126 posts, 1 likes
    Pearson 424
    US East Hampton,NY
    Thanks all, especially to Jim in PB( I wish I was in PB this am-- 20 degrees and WINDY here on Long Island!) for some great info on belts! and to Ranger_12 for NAPA specific info.
    My Gates A43 Belts were a fine fit-- in fact they have lasted over 15 years driving my Ample Power 120 amp alternator. It's only since I read Maine's article that I figured I would replace the belts since I have the alternator off to clean up the salt water spray damage(turns out it was not too bad at all). I saw Maine recommended the NAPA Premium XL so that's the one I was searching for. Maybe I just replace my Gates with the same belt as before!?

    Another question is whether a notched belt is better suited for driving a high output alternator. The answer would help determine which brand/model I should go with.
     


  7. Ranger_12

    Ranger_12

    Joined Mar 26, 2014
    34 posts, 6 likes
    Macgregor 25
    US Kaw Lake Oklahoma
    If the fractional horsepower belt (A43) was working for you just get a 4L450W which is a heavy duty 1/2 X 45 inch belt as long as you don't want a cogged belt . FYI an A belt is 2 inches longer than the part number. Gates makes NAPA belts. Carry a spare.
     


  8. jssailem

    jssailem

    Joined Oct 22, 2014
    7,825 posts, 3,136 likes
    CAL 35 Cruiser
    US Salem, Moored Port Everett WA
    That sure sounds like a straight forward solution. The last belt lasted 15 years. What is the saying... If it ain't broke don't fix it..
     


  9. Peter Mahr

    Peter Mahr

    Joined Jan 14, 2019
    2 posts, 2 likes
    Coastal Recreation Balboa 27
    WindDancer US Portland OR
    Something that has not been mentioned is pulley rust. My Balboa 27 w/Yanmar 2GMF started showing lots of belt dust with a chronically loose v belt. I would tighten it every 20 hrs until there was no more alternator adjustment, and then buy a new belt. It turns out that on seldom used boats, the pulleys rust and eat up v belts. My local Yanmar dealer suggested the only fix is to replace all of the pulleys. I did remove mine, cleaned them up with emery cloth, and repainted them. Have not used them for a season so have not report on effectiveness at this point.
     


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  10. Garbonzo

    Garbonzo

    Joined Dec 4, 2018
    3 posts, 1 likes
    Balboa 27
    NA US Denver
    You have a Balboa 27? Oh what a wonderful boat. Off topic so won't go on but would like to chat sometime. Not to many around.
     


  11. Peter Mahr

    Peter Mahr

    Joined Jan 14, 2019
    2 posts, 2 likes
    Coastal Recreation Balboa 27
    WindDancer US Portland OR
    We have 3 Balboa 27's on the Columbia River in Portland OR. We are all friends and would love to talk to other Balboa owners. pmahr1@gmail.com.
     



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