That's an interesting observation.
The most common thing that will cause the diodes to pop in your alternator/regulator is if you open-circuit them. In other words, disconnect the charge line from the battery bank while the alt is spinning. This will only happen if the switch turns one circuit off before the other is turned on. The four way switches commonly fitted to boats don't do that. They always make the second circuit before breaking the first.
If the switches you get in the US are different to that then they must be custom-made for the American market just to piss you guys off. I can't recall in thirty years of boating having a four-way switch that breaks without making first and all the switches I have had have always been made in the USA and the only time I've ever blown diodes is when SWMBO has turned the switch from One past Off to get to Two.
Or else I've had 30 years of charmed boating :-)
I have seen some boats that have a bank of separate switches to switch this on and that off and then if you follow the wrong sequence you'll have problems. But a four-way? Not in my experience.
Last edited by Omatako; 04-15-2007 at 12:16 AM.