Re: shore power
There are a lot of differing opinions on this, depending upon knowledge and personal experiences. Safe electrical practice says you should always maintain a ground path back to the source of the electric power. All components that could become enlivened by an accidental short (including your pontoons) should be bonded together and connected to a grounding conductor. This ensures that when such a short occurs, a fuse or breaker will immediately sense it and "clear" the fault. You normally can't get a shock from grounded metal parts.
However, simply connecting the ground bus on your boat to the grounding conductor from shore makes your boat's metal parts an extension of the shore power's grounding grid. Typically, ground grids on shore often carry "tingle voltage" that most times harmlessly conduct through the soil. Tingle voltage in water is a more serious matter. Swimmers are vulnerable to even small voltages. Additionally, a small voltage potential difference between your boats metal parts and the water can very quickly cause severe corrosion damage from electrolysis.
Leaving your boat's metal parts ungrounded eliminates the likelihood of electrolysis, but may kill people both on the boat and in the water when a fault occurs. The safest solutions will cost you some money. The best method (and likely the most expensive) is to install an onboard marine isolation transformer. Properly wired, the circuits on your boat are derived only from the isolated secondary winding of the transformer. The metal parts on your boat are ground referenced such that electrons from any electrical shorts on the boat return to your onboard transformer only and have no interest in travelling back to shore or to this dirt ball we're standing on.
A second method (and somewhat less expensive) is to trade the transformer for a "ground isolator". It is connected between the shorepower ground conductor and the metal parts on your boat. Essentially, it directs electron traffic, supposedly providing a safely grounded boat without electrolysis. How well it works may be the subject of differing opinions. Here's a site that may help. The last few paragraphs are more specific to the issue.
BoatUS: Seaworthy
Here's a site discussing the issue of tingle voltage on land as it affects dairy farmers.
Dairy Cattle - Stray Voltage Problems in Livestock Production
- Grandad
