<Scott wrote......Finally, what do you think of electro optical isolators for the GPS and other serial interfaces? Easier to simply convert to RS232 physical connectors and disconnect? And finally, component or composite video?> Perhaps there are some opti isolators that are rated a thousands of volt but I doubt it. Most are designed to eliminate ground loops and provide "low" voltage isolation. Again I have to believe that you need to keep it out of the boat. Once inside then all of man's efforts will be fried in the EMF display that the current/voltage of a strike will broadcast within the boat. We recently were involved in a lightening strike claim in Venezuela. This on a sailboat sitting on Jack stands in a boat yard. The lightening strike happen to be observed by me purely by chance sitting in the pilothouse of Swan Song watching the strikes in the close area. This one was some 200 yards for us. The strike hit the mast head vaporizing the antenna and wind instrument and then a big puff of smoke as the backstay SSB insulator exploded. Then we don't exactly know where it went but there were surface burns on the hull between the bronze thru hulls and the closest jack stand. In the rear stbd quarter below the waterline there was a burned hole the size of a dime with arc traces to another jackstand. We surmised that the charge was therefore inside the boat looking for ways to equalize the ground/sky potential of the strike. This boat was fully bonded and had lightening protection as best that could be provided. The small hole in the hull turned into a platter sized area of charred delaminated fiberglass/resin. We couldn't see why it chose this area of major exit vs. any other but so be it. Ultra sounding the entire rest of the boat's hull showed no other areas of concern. The area was repaired and the boat launched to check on the systems aboard. Virtually everything from the VHF/SSB to all the air conditioners, generator, engine electrics, electric toilets, on and on were dead or limping. Basically it needed a complete refit of the entire electrical system. Not easy to do in a 58' production sailboat. So here is a recent first hand case of what the huge amount of current/voltage can do. Granted this boat was on the hard but the keel which was the lightening ground was 2" from the saturated ground beneath it. Why the potential inside the boat decided to take many alternate paths to relieve the potential difference remains a bit of a mystery. I doubt if a few opti isolators or even disconnecting the power leads unless completely removing the units from the area of the incoming wires would have saved these devices. My concern with these discussions and some of the papers and info that we all can look at and read is that we may think we have a solution to the effects and danger of lightening strikes. I submit that no matter what course of snake oil that you apply to the issue it is still snake oil. If Mother Nature decides to lay one on you directly the outcome will vary and it will not be pretty and not what it said in your "manual's" troubleshooting section. If you are still of a conscious mind and can deal with what ever has been dealt out great. If not then what an adventure up till then ;-) As always YMMV, Cheers Dave & Nancy Swan Song Roughwater 58 Caribbean Cruise '07