"Darn good idea, Larry. Even if you aren't messing
with a higher voltage battery. And put it in ths ship's
wiring. As I discovered, not everyone will use the
same connector with the same polarity."

A minor problem with this approach is that there will be a constant voltage
drop in the line. This is normally no concern, except when you are down to
the low end of the battery range. Then, you have just increased the minimum
voltage by .5 volts.

You can avoid this problem by connecting the diode differently. In this
case, you would connect a diode across the radio. Connect the cathode
(banded end) across the + and the anode across the - . The current capacity
of the diode must be greater than the fuse or circuit breaker. Make sure
there is a fuse or circuit breaker in the line before the battery connector.

If the polarity is correct, the diode will be invisible - hence no voltage
loss. If the polarity is backwards, the diode will short out, blowing the
fuse or circuit breaker. Opposite polarity voltage will not exceed about .5
to .7 volts, which will not damage the radio.

Colin