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Start Battery/Tachometer


JohnC62's Avatar
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Join Date: Jan 2002
Posts: 71

05-04-04, 06:45 PM   #1  
Start Battery/Tachometer

I have a 1995 Calun Bass Boat w/ a Johnson 112 SPL motor. I was stranded with a dead start battery. I disconnected my troll batteries and used one of them to start my motor and I was in the process of reconnecting the start battery while the engine was running and all of a sudden my warning horn went off and my tachometer started smoking w/ the smell of electrical burning. Did I really mess something up? Or is this w afluke and only need my tachometer replaced?

Thanks,

John

 
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jughead's Avatar
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Join Date: Oct 2003
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05-05-04, 05:04 AM   #2  
It wasn't a good idea to replace the start battery with the engine running. There's a good chance that you fried the tach. With all batteries disconnected your electrical system voltage probably went to 18 volts or more. The 12 volt electrical stuff wouldn't like that. What were the circumstances when your start battery went dead? The other possibility is that there's something amiss with the tach and that's the reason the start battery went dead, but that's a long shot.

 
JohnC62's Avatar
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05-05-04, 05:41 AM   #3  
Thatnks. SO you think just the Tach is shot now and nothing else?

John

 
Ed Imeduc's Avatar
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05-05-04, 10:20 AM   #4  
Im with Jug here . You dont change a battery while the engine is running.Could carry jumper cables with you.Id ring or Ohm out all the wires before I started it again just to make sure.

ED

 
jughead's Avatar
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05-06-04, 08:27 AM   #5  
The big question is why do you think the battery went dead and left you stranded? Does your alternator charge the battery with the engine running? A shorted diode in an alternator can cause the battery to discharge with the engine off and then will prevent the battery from being properly charged after you start the engine. I'm only guessing here as I have few facts to go on. I would say that bad diodes are rare, but it can happen. If you have a voltmeter and an ammeter I'd be doing some checking on the electrical system. In the mean time I'd just carry a spare battery and some jumper cables until you can get the situation sorted out and are satisfied that everything is back to normal.

 
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