Ok, this is coming from a guy who gets shocked by beeper batteries. I understand that the Dc ground on a boat electrical system is usually to the engine block, and the ground occurs through the shaft and into the water. I just read in the archives that it is not advisable to connect the grounds from the thru-hulls to the engine as well. Therein lies my confusion, a ground is a ground right? If the thru hulls are all connected by a common ground wire, then what good are they if they are not connected to the electrical system, I assume to help disperse energy, like a lightning strike. More gound surface = better dispersal of excess energy, Right? Any help in explaining yet another mystery (in laymans terms) would be greatly appreciated. I just finished rewiring the whole boat, and no smoke, sparks or fire (Puffs out chest), about 300 crimped, soldered, and heat shrinked (is that a word) connections, and everything works. Not a wire (except for the bilge) below the water line. What a task!