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Thread: One-wire Alternator

  1. #1
    Hotcrusader76
    I had a deep thought today that has got me wondering... idea
    We spin these big blocks all day long at 5K plus...sometimes 6-7K (don't I wish )....
    How fast is your alternator spinning? Don't most Alts. come with 3:1 ratio pulleys? Should I be cautious on purchasing certain versions.
    The reason the question came up is because I am replaceing mine so that the new motor isn't getting it's style cramped by a rusted out alternator.
    Which brand should I use and which ones should I stay away from? Are there high RPM spinning types Alts.? Please advise. frown

  2. #2
    Senior Member
    Join Date
    Jun 2009
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    10,871
    Ty, this is one big advantage of our direct drive kit off the end of the crank on a Chevy (if you have space for it). Turns the alt at crank speed and keeps from over-revving it. That's one reason a lot of the ski race boats run them. Hi rpm for long periods.

  3. #3
    HighRoller
    When I had a high rpm street/strip engine in my car I had problems with the belt coming off so I found a large diameter pulley that underdrives the alternator.I believe it was made by either moroso or Mr gasket and was made of aluminum.Worked like a charm!!Try a speed shop or somewhere like that.

  4. #4
    Hotcrusader76
    Rexone:
    Ty, this is one big advantage of our direct drive kit off the end of the crank on a Chevy (if you have space for it). Turns the alt at crank speed and keeps from over-revving it. That's one reason a lot of the ski race boats run them. Hi rpm for long periods. Mike,
    I don't have room for that kit. This can't be rocket science here , I just want an alternator that isn't going to cook when I rev out close to 6K. What alternator would you recommend from Rex? Otherwise one of the Summit/Jegs powdercoated one-wire jobbees works just fine.
    What's your take on this?
    ~Ty

  5. #5
    Senior Member
    Join Date
    Jun 2009
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    10,871
    Normally the Prestolite Marine Alternators work very well and under normal recreational use we don't see any RPM related problems that I'm aware of. If your running for extended periods at high RPM I would persue getting a larger pulley for it to slow it down some.
    Most automotive (and marine for that matter) alternators were designed for going down the highway on an engine turning rougly 2500 RPM (alt speed would obviously be higher with the small pulley that's typical). If you run your boat engine at 5500 for extended periods common sense would tell me it would be prudent to slow the alternator down some. My concern would be bearing speed (I don't know what the bearings are rated at)... just assuming that if they're in a unit designed for say 6000 RPM sustained they're probably not rated for 15000 RPM.
    Just my guess as I'm not an alternator builder. Like I said, its kind of a grey area because we really don't hear much about alternator over-rev problems.

  6. #6
    Hotcrusader76
    Then I must assume it doesn't matter much. I suppose I'll look into a good alt. and just underdrive it some with a pulley.
    Thanks Mike for your insight on this.
    ~Ty

  7. #7
    OMEGA_BUBBLE_JET
    Ty,
    I have a one wire GM alternator and have run it for 3 seasons with no problem. Standard crank pulley and standard altenator pulley. When I first put it on I had a problem with it pitching the belt. when I switched from a 15mm belt to 13mm belt the problem went away. 13mm sits deeper in the groove. Haven't pitched a belt since and I run mine at 5200rpm but not all day. I usually cruise at 3500rpm.

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