A couple of years ago, the voltmeter on my boat began to read high.
Over a few weeks time, it ended up reading 16 volts at idle and nearly
18 volts at cruise. The motor is a 1999 model Johnson 150 outboard.

It was due for service, and I mentioned it to the dealer. They said
the voltmeter was bad, replaced it, and it again read correctly.

Now it doing it again. This time the battery was going bad, so I
thought maybe that could ahve something to do with it. I replaced the
battery last weekend, and it still read high, just like before.

I'll be doing some investigating with a multimeter next time I'm out
to make sure it's really the meter, but I was just wondering... is
this fairly common? The boat stays covered in a slip except when
we're using it, so its not like it sits out in the weather and is
abused. It just seems that these factory installed voltmeters are
dying.