Unique Products for Your Boat
  • CMI-HD125-ER - 125A 3.15" Saddle Mount, 1" Foot or 2" Foot Heavy Duty Marine Alternator

    $629.00 $529.98


    We Do Not Ship Alternators Internationally

    IMPORTANT:  All CMI Alternators are custom built and may require a short lead time. If you are unsure about fitment or compatibility please use the "Contact Us" tab at the top of this page.

    The CMI-HD125-ER

    Ample Power recently closed its doors leaving many of its alternator customers without a direct replacement option. We have had many requests for Ample Power replacement alternators so the CMI-HD125-ER has been introduced. It has also been heavily heavily upgradedin the process. The CMI-HD125-ER an exact replacement for the Ample Power small frame alternators, such as the 4023-S, and it's available in a Yanmar 3.15" saddle mount, 2" foot or 1" Motorola style foot mount (please specify mount type when ordering).

    Never settling when it comes to performance Compass Marine Inc. has taken the Ample Power small frame platform to a whole new level of quality. Ample Power used 200V 50A diodes, we are using 400V 75A diodes. This means the alternator runs considerably cooler. We have also upgraded to using the finest USA made magnet wire available. It has a much higher temp tolerance rating than its predecessors.  We also noticed localized heating for the B+ stud so we now build these with bronze B+ studs as it is significantly more conductive than steel. Once again, helps minimize excess heat developed in the alternator..

    The CMI-HD125-ER is the best and most heavy duty small-frame alternator we build. Because we have no middle-man markup, and we sell direct to the end user, the CMI-HD125-ER saves you over $250.00 when compared to 120A Balmar 6-Series. The Balmar 6-Series is an excellent small frame alternator, but not all boaters have this in the budget.

    Serpentine Pulley Kit Compatibility:

    A major benefit to the CMI-HD125-ER is that it can be used with an AltMount/Balmar serpentine kit with minimal to almost no alignment issues during set up. See image above with a CMI-HD125-ER installed using an AltMount serpentine kit on a Yanmar 4JH3-HTE.

    External Regulators:

    We can package this alternator with a Balmar MC-614H or ARS-5H regulator or a Wakespeed WS500 or WS100 external regulator.. We strongly recommend setting the Belt Manager feature to level three or four when setting up the regulator. It's also mandatory that an alternator temp sensor be used. Compass Marine Inc. will never make the lofty (bogus) claims Ample Power made about these alternators being constant duty. We choose not to grossly mislead our customers. No small frame alternator we know if is constant duty no matter how much a manufacturer tries to mislead you.

    CMI-HD125-ER Specifications:

    The CMI-HD125-ER comes standard with tachometer output (stator tap) for diesels that run the tachometer sense off the alternator. Not all engines drive the tachometer from the alternator, but most Westerbeke and Universal engines do and many Yanmar engines do as well.


    • Intended to fit many diesel engines that use a 1" foot, 2" foot or Yanmar 3.15" Saddle Mount
    • 125A cold rated, 106A hot rated with excellent high idle performance.
    • Hand wound stator (wound here in the USA) of 14GA extreme duty magnet wire = higher temperature tolerance.
    • Precision machined rotor and slip rings for greater contact at all RPM.
    • High performance 400V 75A rectifier diodes. (same diodes used in massive 200A+ alternators costing 5X as much)
    • Directional (Clockwise) Chrome Fan (If you need a Bi-Directional fan please let us know)
    • Billet Machined Steel Pulley - 2.6" Diameter X 1/2" or 3/8" 10mm Belt Will Also accept an AltMount J10
    • Brushes are high copper content, not run of the mill cheap carbon brushes.
    • High copper brushes yield superior conductivity and considerably longer brush life.
    • Ready to accept an external regulator. We recommend only Balmar or the WakeSpeed WS500 regulators.
    • OPTIONAL - Isolated ground for steel or aluminum boats or for using a shunt in the negative path.
    • Stators & Rotors Wound in USA
    • USCG Certified - Gas or Diesel Engines
    • 5/16" Silicon Bronze B+ Stud
    • 5/16" X 18 B- Bolt
    • 5/16" X 18 Adjuster Ear Tapping
    • 10mm Foot Mount Hole (Hitachi/Yanmar Model)
    • 1/2" Foot Mount Hole (Motorola Model)