110 volts to a boat.....

[Frank]

probably a dumb question...but  ???    I can do fiberglass repairs, work on engines but I just don't understand electrical. So....    I see when boats are "plugged in" to shore power...they have grounding plates, all the trhru-hulls are grounded (if done right), even the prop shaft can have a seperate ground. So...my question is: what happens on a simple "sailfar boat" if you plug in to shorepower and simply run an extension cord to the boat for a lil ceramic heater or toaster??  After seeing how things are all grounded for shore power I assume this is not good? Who What Where When Why???   Who has more knowledge on this??

[Tim]

Well, nothing bad will happen unless you jump in the water holding the extension cord.  ;D My sailboats have a charger that gets plugged in when in a marina. I have also used it for a heater. Observing the usual precautions will keep things safe enough. 

[CharlieJ]

That's what I do aboard Tehani . She has zero 115 wiring. I have a GFI inserted  in the extension cord, and make sure the cord doesn't get into the water.

Never had a boat with AC wiring, including my 35 foot tri

[Frank]

Thats what I thought.....but why all the grounding wires on "shore power" boats?? What am I missing?

[CharlieJ]

I dunno- since never had shore power, never paid any attention

[Tim]

It is different when you have mixed devices (110 and 12v) wired directly into the boat. There are requirements to keep the circuits isolated.

[Godot]

I think that all the fittings being grounded has little to do with the AC system, but rather is an attempt to keep everything at the same potential to minimize galvanic corrosion. Lots of boats (mine included) have above the water fittings "grounded" also. I don't think there is any galvanic benefit to this; but I think it was generally considered the way to do things at one time. Perhaps it will help in the event of a lightening strike (my mast and standing rigging is bonded through the backstay). Perhaps not.

My opinion: it is probably a good idea to bond below waterline fittings to each other to try and limit galvanic corrosion. Some folks make the argument that this actually increases corrosion, so your mileage may vary. If my boat wasn't already set up this way I probably wouldn't bond the above waterline fittings. Galvanic corrosion does not happen quickly (unlike stray current corrosion which I understand works much faster...no experience here), so if you inspect your fittings every year or two you will probably discover if there is any corrosion before it becomes a real problem.

My AC system is probably more involved than most folks here, but still less complicated than the typical yachty. The AC system is completely isolated from the DC system, and is built pretty much in accordance with the guidance in Don Casey's "Sailboat Electrics Simplified" (I highly recommend this small, very useful book) with the exception that I have not yet installed a galvanic isolator. Maybe next year.

I rewired almost everything a couple winters ago. Casey's book was my bible for this difficult, time consuming process. I found that a great many of the original wires in the boat were undersized or corroded. Some were grotesquely under sized (the wires going to the wash down pump-an extravagance I love-I believe was wired with 16AWG before I changed it to 10AWG). I feel much better about everything and trust the whole system completely now. It is well worth learning how things should be and at least inspecting to figure out how things are.