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Old 03-06-2018, 16:27   #16
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Re: Replacing very old alternator

An internal regulated alternator on a boat can not handle the heat. You will toast a 100 amp single wire Delco in no time on a cruising boat with only 3 or 4 batts.
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Old 03-06-2018, 16:52   #17
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Re: Replacing very old alternator

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An internal regulated alternator on a boat can not handle the heat. You will toast a 100 amp single wire Delco in no time on a cruising boat with only 3 or 4 batts.
Not true for all internal regulators, the Auto ones downrate via thermistor so they don't heat up. But then the point of a high output alternator is lost.
I will concede that some Delco clone ones WILL heat up, presumably to melt winding insulation or diode damage level.
I have tried a Delco clone (120A)and it heated badly in a few minutes .
Switched to a cheap as chips Bosch & external regulator- Doesn't heat at all delivering
whatever current battery (and belt) will allow.
The bosch Does have externally ducted air thru a factory cowl.
Cost, $50. Probably doesn't need the external reg.
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Old 03-06-2018, 18:20   #18
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Re: Replacing very old alternator

Yes integral cooling design is key, many large-frame type are designed to output 70-80% the nominal (max) rating all day long.

Facilitating active ventilation helps.

Temp sensors are critical if pushing past 50%, and reducing **amps** output rather than voltage.
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Old 03-06-2018, 18:48   #19
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Re: Replacing very old alternator

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Originally Posted by Ecos View Post
An internal regulated alternator on a boat can not handle the heat. You will toast a 100 amp single wire Delco in no time on a cruising boat with only 3 or 4 batts.
Its only 1 batt. (starter)
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Old 03-06-2018, 21:30   #20
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Re: Replacing very old alternator

Doubt whether a start battery would get discharged enough to draw much current from the alternator.
Having a 100A capable alt would be a good backup for the Balmar though, suitably regulated & cooled. (And switchable)
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