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  1. #1

    Default alternator rotation

    The original Motorola alternator on my port engine froze up so I ordered a new 1-wire model (10si style). These alternators seem to have a fan that is oriented in one direction. Unfortunately I think that engine is rotating the wrong way. Anything wrong with just replacing the fan with a bidirectional one?

  2. #2
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    7,340

    Default Re: alternator rotation

    Quote Originally Posted by juryduty View Post
    The original Motorola alternator on my port engine froze up so I ordered a new 1-wire model (10si style). These alternators seem to have a fan that is oriented in one direction. Unfortunately I think that engine is rotating the wrong way. Anything wrong with just replacing the fan with a bidirectional one?
    I understand the the centrifugal fan blades are aimed in the wrong direction for a Rev RH Rotation engine, but generally it's not an issue.
    Is your Port engine not a standard LH Rotation engine ???
    (Industry Standard for LH or RH rotation is as though viewed from the flywheel end)

    If your Port engine is a Rev RH Rotation engine, and if you can find a bi-directional fan for the 10si, go for it!


    Keep in mind the the single wire Delco 10si needs to be bumped up to approx 1,200 RPM, or so, before it will excite.
    Once excited, it will remain excited until shut down again.




    .
    Last edited by RicardoMarine; 08-14-2013 at 07:26 AM.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  3. #3
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    5,598

    Default Re: alternator rotation

    We switched to the Delco alternators years ago....but had more to do than just the fan...

    Yes, I'd recommend switching the fan...visit your favorite rebuilt shop and they should be able to get you the "opposite" fan...

    The other issue we found was the mounting bracket needs to be modified...based on memory, we used a mill. Just make sure you verify the pulley lines up or the belt will come off in short order...

  4. #4
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    7,340

    Default Re: alternator rotation

    Quote Originally Posted by makomark View Post
    The other issue we found was the mounting bracket needs to be modified...based on memory, we used a mill. Just make sure you verify the pulley lines up or the belt will come off in short order...
    Mark, a true Delco 10si should have a very consistant footprint with regard to the mounting ears.

    There are many of these 10si Chinese knock-offs being sold today, and I'm wondering if this problem is limited to these only.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  5. #5
    Join Date
    Oct 2009
    Location
    New Haven, CT, USA
    Posts
    541

    Default Re: alternator rotation

    Off Topic, I have a good used alternator (50 amp Mando) and CW and CCW starters from my 454's if anyone is looking... Bob

  6. #6
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    5,598

    Default Re: alternator rotation

    The delco 10SI mounting is different from the motorola mounting...no imported junk was used

  7. #7
    Join Date
    Mar 2009
    Location
    Portland, Oregon,
    Posts
    7,340

    Default Re: alternator rotation

    Here's a typical 10is mounting ear and tensioner mounting ear.





    The 10si should mount in place of this style..........




    .............. or this style.... Yes/No???




    However, I have seen where the 10si pivot bolt hole is 7/16", and requires either a sleeve bushing, or the bracket drilled out to 7/16".
    Last edited by RicardoMarine; 08-15-2013 at 08:09 AM.
    Rick ... aka Ricardo
    Portland, Oregon
    28' SDN F/B w/ twin Volvo Penta 5.7L DP's

  8. #8
    Join Date
    Sep 2008
    Location
    Maryland - USA
    Posts
    5,598

    Default Re: alternator rotation

    A 5" small case alternator with a 2" spool usually interchanges with a "like sized" package...what I had a originally a 1" spool setup and there needed to be some clearance made to accomodate the 2" spool...Yes, same for the pivot hole size but that issue should be obvious.

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