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Overcharging 18+ volts?!

rcpistonheadrcpistonhead Member Posts: 4 ✭
in Electrical Discussions
Last weekend on the lake I was boating around when I noticed the volt gauge pegged around 18 volts. I slowed down to idle speed and the voltage went back down around 13v. I idled around for a while and the voltage stayed around 13v. Then, as soon as I gave it some throttle and the RPMs raised, the voltage spiked around 18v again. When the voltage spiked I could hear the alternator whining like it was working hard. Then when I slowed back down to idle speed the volts dropped back around 13v and the noise stopped. I didn't have a volt meter with me so I couldn't check out put at the batteries and alternator but I know the voltage was high because the amp for my audio equipment was shutting off / going into safe mode.

Any ideas what could be causing the overcharging?

Thanks!
Ben Weaver
1998 Rinker 212 Festiva
Mercruiser 5.7L TBI
Alpha One gen 2
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    floater212floater212 Confirm Email, Member Posts: 121 ✭✭
    sounds like the regulator, it control the voltage and amps needed.
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    rcpistonheadrcpistonhead Member Posts: 4 ✭
    floater212 said:
    sounds like the regulator, it control the voltage and amps needed.
    That was my initial thought as well. I took out the alternator and took it to Napa to have it tested. It tested good but I had them rebuild it anyways. They replaced everything - brushes, bearings, regulator, etc. It took them a few days so in the mean time I bought a new alternator and installed it. (there wasn't a core on the new alternator so I will keep the original that was rebuilt as a spare). I was also running Optima Red top batteries that I exchanged for new Optima Marine blue top batteries. I haven't had a chance to run it on muffs or on the lake yet, but I am going to the lake on Sunday and will report back.

    Just out of curiosity - Is it possible a bad ground could cause this? I haven't checked the grounds yet but I will tonight.

    Thanks!
    Ben Weaver
    1998 Rinker 212 Festiva
    Mercruiser 5.7L TBI
    Alpha One gen 2
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    rcpistonheadrcpistonhead Member Posts: 4 ✭
    A new alternator has fixed the problem. The voltage regulator in the original alternator was bad.

    Thanks!
    Ben Weaver
    1998 Rinker 212 Festiva
    Mercruiser 5.7L TBI
    Alpha One gen 2
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    raybo3raybo3 Administrator Posts: 5,459 admin
    Glad your all fixed up. Happy boating....
    2002 342 Fiesta Vee PC Point Of Pines YC Revere MA. popyc.org     raybo3@live.com
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    sflippensflippen Member Posts: 5 ✭✭

    In the future..... I take my alternators to someone who can test them completely. Napa has a standard program that only test to see if it put out vooltage and amps but does not test for load conditions such as bad batteries.  I went through 3 alternators all tested good on their equipment but were bad when tested properly.

    FLIP'N OUT

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