Charging Problem

RJBdaddy

Recruit
Joined
Aug 31, 2010
Messages
2
Have a Merc Scorpion 5.7L - replaced batteries 3 seasons ago....charged them both prior to this season, started fine but when in idle the gauge is showing a 'drain' dipping below 12v - when running at normal speed/revs...gauge pops back up to showing charging....but even if run for a length of time as soon as it goes into idle the gauge shows a drain....looking for advice...is it alternator?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
51,207
use a known good meter and test, dont rely on the dash gauge

take the alternator off and have tested.
 

RJBdaddy

Recruit
Joined
Aug 31, 2010
Messages
2
Thank you, I was not aware the gauge may not be reliable. I performed test on batteries standalone and one was perfect, the other maybe does have a dead cell as it was sitting at about 10.25. Once running I ran test on both and they were at the 12.7 range
 
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