On Thu, 12 Apr 2007 14:22:04 GMT, Charlie Morgan
wrote:

You may have trouble finding a zener diode rated at enough amps,
though.

In actual practice the zener diode is usually wired in series with a
resistor sized to limit amps at a safe level. Transient spikes
contain very little actual power in electrical terms, only high
voltage which zener diodes shunt to ground.

That said, I've been operating boats with sophisticated electronic
systems for many years, have never taken precautions when starting the
engine(s), and have never experienced any transient related failures.