Jim wrote:
"Short Wave Sportfishing" wrote in message
...
On Wed, 10 Jan 2007 14:38:52 GMT, "Jim" wrote:


"Jack Goff" wrote in message
news 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.

!6 to 19 volts sounds like an open battery circuit. Clean and tighten the
battery cable terminals at both ends, then do a voltage drop test on both
battery cables. Replace wing nuts with hex nuts.

Now there is a discussion worthy of some debate.

Why?
Here's my theory. Outboards have a coil that produces AC when it passes a
magnet. The AC is converted to DC by a bridge rectifier. That's pretty much
the complete charging system. Any regulation that is done, is done by the
battery. No connection to the battery allows the charging system to produce
maximum volts and no amps. A fully charged battery connected to a running
engine shouldn't be showing any more than 14 to 14.5 volts. Any more will
boil the water out.

You're correct, Jim. But why would it ruin a guage?

Jack said that the dealer replaced the guage, and it temporarily cured
the problem.

Speaking of outboards, that is , older ones. I've always wondered why
they had such a primitive charging system? very low amperage output,
with cheaply made and finicky stators. About like a Briggs & Stratton.