Good START of the discussion people !
I had suffered a lightning strike 4-5 yrs ago as well. I was the only boat in the mooring field for ~75yds....and was the 'most attracitive' target the static charge!! It vaporized my VHF antenna, the pressure wave blew my Windex wind indicator apart , fried my VHF radio and 2 bilge pumps, and shot a couple of fuses / fuse holders across the cabin from the power panel.
Yes, I did have a grounding cable attached to the mast...a #6 awg crimped with large spade lugs to ensure good electrical continuity at both ends (mast foot and the keel bolt). No, I did not take an installed resistance check from mast to keel bolt, but periodic visual inspections yielded no corrosion / high resistance connections, and my PM is to dismantle, clean as necessary, and replace as necessary, then reinstall yearly.
BTW, it's not ONLY the strike itself, but secondary (induced) current IS serious...i.e., essentially all of the "non-direct circuits" in the boat are involved in the lightning strike as if they are a secondary winding of a transformer. And, as such, when the voltage is high, as in a lightning strike, the current / voltage that is produced in these secondary circuits is directly proportional, but the amount of induced current / voltage drops off exponentially as the distance away from the lightning actual travel path increases.
Now, granted this induced current / voltage is produced from a DC spike and acts like a PULSE to the secondary circuits on the boat, but nonetheless, all those electronic gizmos contain printed circuit boards, IC chips..etc, and WILL be affected. They are not designed for the "higher VOLTS" range, but rather MILLI-volts or less. They will certainly get flashover arcing, to various degrees, on the circuit boards / chips / wiring...thus frying various parts, and good luck trying to repair individual circuit components these days !!
It boils down to "black box" replacement of the entire affected unit(s) (VHF, GPS, bilge pump, etc...) because gone are the days of diodes, resistors, capacitors, inductors and transistors, where one could troubleshoot and service some equipment yourself.
I did all of the repair / (mostly)replacement work...cost ~$800. I got off lucky with NO hull damage.
Once again, good discussion topic...!
I encourage your inputs, perspectives, and ideas...!