"Steve" wrote in message
...
I had thought about the capacitor but wasn't sure if it would help much
with the really big current loads which are all motors (bilge, toilet,
fresh water, gray discharge etc.). Would a 100uF cap actually be enough
to cope with such a large inductive load?

That is way to high. Use 1uF at most, together with a series resistor of 10
ohm or so. Having a large capacitor will kill the switch when closing. The
loaded cap gets shorted....

In a DC system, you can also put a diode across the switch, in reverse. It
blocks the current from the battery TO the load, but any induction which
creates the opposite voltage across the switch, opens the diode and prevents
any arcing.

Meindert