Thanks for the expert advice.. now a further clarification..
Having started the engine on #1.. and motoring
out of the harbour.. say 10 minutes.. is it advisable/safe
to switch to #2 on the Master Switch.
Or must one first turn the engine OFF? To protect the alternator.



John Cairns wrote:
Your switch should be a "make before break" type to prevent damage to the
alternator. That being said, unless you have a device like a "zap stop"
installed it probably is a good idea to turn the engine off before switching
batteries, just in case.


It's easy enough to test whether the battery selector switch
"makes before breaks" with a multimeter or continuity
tester. Good thing to know for sure. Personally, I have
never fried an alternator but have also always put a sign
over the battery switch and had a strict "hands-off" policy
for crew/guests. Lots and lots of people have fried their
alternators, so the danger is certainly real.

10 minutes charging isn't really going to make a difference
so you might as well leave the switch on your start battery.

You might also consider getting a battery combiner. This is
a relay that brings both batteries in parallel when there is
charging current, and isolates them when there isn't. This
means that both batteries get charged when the engine is
running, whatever you do with the switch.

Fresh Breezes- Doug King