"Ernie" wrote in message
. ..
Is it normal for the battery gauge to read 16 when the boat is in
operation? The gauge only goes up to 18. The battery will be a year old
next month. Should I be concerned?

Ernie - More accurately, this is a volt meter, not a battery gauge. This is
nit-picky, yes, but an important distinction. When the motor's running, it
measures the output of the charging system, not the state of the battery
itself. Therefore, it's not the battery that is possibly "wrong" it's the
charging system. I say "possibly wrong" because...

As others have mentioned, the first guess is that your dashboard gauge is
inaccurate. You can test the battery, charging system, and therefore the
gauge, by getting a decent digital multimeter. The meter doesn't have to be
expensive, but I recommend digital because they're easier to read. Set it
to the volts DC scale, and test the charging system by putting the
multimeter leads on the main battery cables while the motor is running. As
mentioned, it should read "around" 14 volts (13.8-14.2).

When the engine is stopped, the meter (and your dash gauge) would simply
test the output of the battery itself. A fully charged 12 volt battery is
12.6 volts. This varies a little higher if it's freshly charged (it will
"settle" at 12.6). But, if it's actually at 12 - it's almost dead.

You can get a very cheap, little tester that will indicate (with various
colored LED's generally) if the charging system and/or battery is good or
bad. These LED's are, of course, set to indicate the ~14 threshold for the
charging system and the ~12.6 volt threshold for the battery itself. But a
multimeter is a handy tool to have and worth spending a few bucks on. I
carry the little cheap tester in my small tool box though.

Beyond that, I don't know how to trouble shoot or fix. I don't know from
rectifiers, stators, regulators, etc. But if you find that the multimeter
shows a good charging voltage of around 14 when the engine is running, you
can be pretty sure your gauge is bad, and you need to buy a new gauge. You
can find a lot of options on line from OEM to aftermarket and should be able
to exactly, or closely match your existing gauges. I'd suggest you
temporarily test the gauge before actually installing it. Gauge
installation is a pretty easy DIY if you're so inclined.

Cam