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Thread: Perkins 4-107 Alternator

  1. #1
    Join Date
    Dec 2003
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    Sound Beach, NY
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    Default Perkins 4-107 Alternator

    On monday my alternator was working well, until it went from charging the battery to draining it. The amp meter dipped farther left than turning on every electric part on board. Disconnecting the alternator stopped the drain, making me think I want a new one. The alternator is a Delco Remy 10DN three wire external regulator. Has anyone had experience suggesting I should do something other than replace the alternator?

  2. #2
    Join Date
    Apr 2017
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    Kailua, HI
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    Default Re: Perkins 4-107 Alternator

    Look around your area for a shop that specializes in rebuilding alternators and starters, there are certain to be some. Way cheaper and in my experience just as good. I keep a spare for the boat I run and we regularly swap out while the failed one goes for rebuild and then becomes the spare. Saves the headache of being sure of exact fit for mount, wire harness, and so on. Especially for high output alternators (ours are 135A) the cost savings over new is considerable, and the rebuilds give good service, even in daily use over long periods. The local shop I use does a full rebuild every time, bearings and electrics. Sounds like yours had a diode fail, good call disconnecting it-they can get really really hot if left hooked to a big battery bank.

  3. #3
    Join Date
    Mar 2011
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    Mukilteo, WA
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    3,032

    Default Re: Perkins 4-107 Alternator

    My 4-107 came with two different alternators. The one I use now has a dodge part number I believe. Works fine. I don't think there is anything special about alternators as long as the bolt pattern fits and the spinny part goes around.

    Maybe a benefit to finding an internally regulated unit, I get the impression its easier to fry the old external style. I fried one of mine by disconnecting power while it was running accidentally.

  4. #4
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    Jun 2003
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    Central Coast, Ca
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    Default Re: Perkins 4-107 Alternator

    Update it to an internally regulated unit.
    Alternators are almost generic, many models and brands will fit in the same brackets, and you can get a significant upgrade in output.

    Edit to add: https://www.ebay.com/itm/105-Amp-Hyb...sAAOSwk3Fa~IDZ
    Last edited by Canoeyawl; 07-01-2020 at 12:31 PM.

  5. #5
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    Dec 2003
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    Sound Beach, NY
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    Default Re: Perkins 4-107 Alternator

    Thank you all.
    After consulting an experienced parts guy and mechanic (both auto) and getting a referral from a third who is a longtime boater, I went to a nearby auto electric shop. The guy there suggested the successor to the 10DN, the 10SI. It's another Delco, internally regulated "one wire" alternator with the same bolt spacing. He is going to add screens for fire resistance and rebuild it for a price similar to ordering one online. So all of your suggestions are combined in one solution. Hopefully I'll be underway soon.

  6. #6
    Join Date
    Apr 2005
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    Default Re: Perkins 4-107 Alternator

    When a starter or alternator goes bad, a good auto-electric shop is a wonderful thing. Glad you got it sorted!

    I just have to add that if you are charging deep cycle batteries, a normal regulator (internal or external) will not charge it (them) properly. If you have a separate starting battery - then NP.
    "If it ain't broke, you're not trying." - Red Green

  7. #7
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    Default Re: Perkins 4-107 Alternator

    Thanks, I've thought about that too. I'll ask the rebuilder about it. My batteries are RV style dual purpose.

  8. #8
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    Default Re: Perkins 4-107 Alternator

    Quote Originally Posted by johngsandusky View Post
    Thanks, I've thought about that too. I'll ask the rebuilder about it. My batteries are RV style dual purpose.
    An automotive rebuilder may not be very familiar with deep cycle batteries.
    "If it ain't broke, you're not trying." - Red Green

  9. #9
    Join Date
    Dec 2016
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    EU
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    730

    Default Re: Perkins 4-107 Alternator

    The rebuilder is not interested what you charge with it, he restores function. This is a standard 60A alternator, meaning it will make ~30-40A continuous depending on temperature. You can put whatever smart regulator on it, but the output can only be changed with physical alterations to the alternator.
    Bulk charging is usualally around 0.3C maximum (check your specific battery for specs) and that absortion rate can only be sustained for a short time. Standard automotive regulators can properly charge any "deep cycle" battery, it just takes more time. A 60A alternator with standard regulator is absolutley OK on a battery of up to 200A.

  10. #10
    Join Date
    Dec 2003
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    Sound Beach, NY
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    Default Re: Perkins 4-107 Alternator

    I checked, the original regulator is just an old automobile model. It served well for decades, including the 12 years I have owned the boat. I think the new one will serve well too.

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