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2004lebanshee

Alternator test results....

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So I posted a pick of my boat gauges while the throttle was wide open. Someone commented that my voltage gauge was showing that my alternator wasn't charging.  I did some testing and this is what I found...

Boat off and starting battery only

12.53v

 

Started up boat and left at idle

Battery 13.72 and gauge about 12.2

 

Boat at 2000k RPM

Battery 13.82,  gauge 12.2ish , positive terminal on alternator 14.9 ( connected the negative lead to the house battery negative terminal)

 

Boat back to idle

12.64 battery and gauge at 11.2 ish, positive terminal on alternator 14.52

 

Now I didnt think I hand any problems. I was mentioned by another poster that they thought the reason my 496 alarmed at 5000rpm and 56 mph was that it was reading low voltage. ( he was able to see my gauge in the pic). I think it was the rev limiter.

Is it safe to say the alternator is good and my gauge is off? 

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Does your engine ALWAYS start in1 or 2 seconds of cranking ?  Or does it take longer  ?    Were you using a decent voltmeter to take readings at battery ?   A great way to test if your DCVOLTS are close to being right on the  handheld meter is to measure 1.5 volt & 9 volt batteries.  

The variation between the Alternator output screw & at the battery could be a voltage drop due to recharging the battery from the cranking.

The voltage difference between dash gauge  & battery  could be the meter  aging

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How freeking difficult is it with the CRAPIEST way to build a meter.  They must deliberately make them read so badly. 

The true value of it.  Is to tell you someone has stolen your battery.

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If your setup is like mine and have dual batteries with an isolator you will have about .5 to 1 volt drop through the isolator. That’s normal.  Just an FYI. 

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5 hours ago, CKSNAP said:

If your setup is like mine and have dual batteries with an isolator you will have about .5 to 1 volt drop through the isolator. That’s normal.  Just an FYI. 

I do have the factory isolator with diaods. Thanks.

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I added an amp gauge to my gauges, so I can monitor both at the same time.  Denny

 

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my voltage gauge reads about 2.2 low , also.  my speedo(which is a separate gauge) reads about 4mph when compared to GPS

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Excellent gauge Denny. That one will always tell you when the battery SHOULD be charged up. If you see a creeping up & steady current demand ?  Check it out time. Battery or even a loose connection growing.  Ammeters are a great diagnostic tool..  Just like oil temperature.  The old woody boats had temperature gauges of fluids.    

Love visual analog gauges.  They give a check of themselves & of what they monitor constantly without key pads & scrolling.

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