Your thinking is correct about charging dissimilar batteries hooked in
parallel. You could wind up with one under charged and the other fried. Some
google searching will verify this (for non-believers). I don't think you
will find a marine switch without the both selection. Since you are dealing
with relatively low amperage, you may be able to find another type A/B
switch and then seal it with liquid tape. Just a thought.
--
Bill
Chesapeake, Va


"CCred68046" wrote in message
...
So... rather than replace the old, oddball battery(s), you think a
different
switch is an appropriate fix? Gimme a break!

OK guys, I'm not going into huge detail here, I have done that before with
this
problem. My Johnson outboard has an un-regulated charging system. There
is
really nothing on my boat that uses any current to speak of. Once the
starting
battery is fully charged (very quickly) the voltage go's up to 16+ and
this is
not good. Its much cheaper to buy the switch to let the voltage go to the
trolling motor battery which is usually discharged enough to keep it
"busy"
than it would be to try and put a regulator on it. To further complicate
matters the charging system is only 5 amps so when I used a combiner, both
batteries wound up low (I cant win!). Sooooo, I figure I can watch the
guage
and just flip the switch when the voltage gets too high and let the
trolling
battery have it. At 5 amps it would take it a looooooong time to recharge
the
trolling battery. If anyone else has a better plan I am listening.