ISO boat standards have no requirement to "ground" anything in most cases
DC ground is a misnomer, its a current
return path to the battery
. It may or may not be at earth potential, on a schematic GND and Earth are different symbols. There is no need and in a metal boat an advantage not to to have a earthed DC ground.( or any ground to the hull).
There is a clear advantage in not connecting DC return to earth to AC protective earth wire on a boat. Again ISO does not require it as protection is left to an RCD. so called equipotential bonding is a "practice" that is not actually well though tout for metal boats in particular.
Bonded underwater fitments can cause more trouble then bonded ones and I personally see no point to them in a GRP boat for example. You are actually creating galvanic cell and a route
to potential impressed current corrosion
specifically state that RF ground and DC ground () i.e. DC return) should NOT be connected, any one with electronics
101 can tell you why.
Also I would state that AC earth should not be connected to DC negative , let the RCD do its job, this prevents load dumping into the DC system. ABYC has a shortsighted view of this of course and doesn't allow it because its thinking follows NEC and its shortsighted views on whole house/whole boat RCDs.
RF ground is in effect part of the antenna
system and the seawater makes any excellent counterpoise
, If the hull
is inert, then making it an RF ground ( install those DC blocking capacitors) is a very good idea. If the hull
is part of the DC system ground, consider and isolated route
to seawater, or if not possible separate RF ground point and DC ground point to minimise load dumping and raising the DC noise
floor. By preference I would have an isolated path to seawater, if my hull is in the DC return path
Lightening protection is more then adequate on a metal vessel and needs not to be further covered here , its a distraction
Common mode voltage as a result of lightening are a complicated discussion and beyond most people here. ( and they arnt interested) its a complex subject with a degree of uncertainty of outcome. But its not a problem in the vast majority of people in day to day sailing
be very careful of people that quote "code" and practice to you. Understand that around the world there are all sorts of national "codes" often that directly conflict with each other , ask yourself how that can be and maybe your "code" is wrong ( or not) YMMV.
Look at thing from first principles and remember a boat is not a house.