On May 21, 8:54*am, "*e#c" wrote:
On May 21, 7:17*am, tem wrote:

I have 1986 Mercruiser 170 (mdl MCM 170) w/ 2 battery system. This may
be a dumb question, I'm not a mechanic. My volt meter reads 12.3 on each
battery when engine is not running and 12.2 after I started it. Does
this mean my charging system is not working? Any help or advice is
appreciated.

--
tem

Did you take a direct reading off of the Alternator while engine is
running? Thats where I'd start.

One thing to check, as you have dual batteries, what position is/was
the Battery Select Switch (I would assume there is one) on while you
were doing voltage checks? Depending on who wired everything
originally, well....who knows! You should have about 14.3-14.7 VDC
when the emgine is running above idle and with majow loads turned off.
12 volt batteries are generally concidered to be 100% charged @ 12.7,
3/4 @ 12.25, 1/2 @ 12.2, and so on (readings taken 24 hrs after any
charge/discharge action) I'd check at the Alternator, then at batt #1
(with the batt select switch at Batt1. bhen at batt #2 with the batt
select sw at batt2, then at either and both with the select sw at
"all".
Good luck!
Mike