Skin Effect, amounts etc
Ok so here I go with the professional secrets again.
1> It has to be foil. RF (Radio Frequency) energy travels along the skin atoms in the copper. On some frequencies it only travels in the electrons of the outer two atoms of the skin. Pretty thin. Wire especially marine grade wire has very small conductors bundled together. This is the least amount of skin that you can have in a conductor. So it has to be copper foil.
2> Grounding to the engine block is BAD. The engine block is not going to provide a good capacitance coupling device to the sea water around it. You will on most boats end up with very poor direct bond to the prop, which since RF is AC at big frequencies you don't want. Lets run though that: Bronze prop + stainless steel shaft= 2 dissimilar metals, RF= AC running through it == Potentials for electrolysis corrosion issues. Also having the ground from your alternator which is also a radio due to the way it works, feeding it's signal directly into the ground of your ssb should your engine be running while you are trying to listen to the weather, is not a great idea for noise.
3> Going over tanks is good but only if they are metal. A metal tank with the copper strap attached to it is a good thing. (NOTE NOT IF THE TANK IS ALUMINUM, the COPPER STRAP WILL EAT THROUGH THE TANK!). This gives the ground plane a larger area of ground plane which is what we are trying to do. It also in most cases gives us a cool effect called capacitance coupling to the water. (This is sometimes disputed by different people, I am on the side of capacitance coupling. The makers of sintered bronze blocks are not, cause well they make money if they can talk you into a sintered bronze block). ((RARE exception the sintered bronze block is some boats, maybe 1 in 300 or so just can't seem to get a descent ground no matter what you do. In those cases occasionally a sintered block will help with the little tiny extra metal that it provides in contact with the water.) In most boats they are just two more holes below the waterline that don't do anything except tempt fate.
3a> By all means grab 1 thru hull. 1, not all of them. You are making an RF ground not bonding the boat. The thru hull does not suffer the same fate as the prop, cause it is only one metal. Oh yeah it goes without saying, but lets say it anyway, plastic thru hulls, or thru hulls above the water do nothing for you. Don't bother connecting to them
4> How much copper you need. Most boats need about 25-50 feet of 2.5 to 3" copper strap. Toward the low end if you can go over the top of a tank, toward the high end if you can't. More than that and all you are doing is cutting your hands up every time that you go to get something out of a locker.
5> All this is for a modern automatic antenna tuners which should be installed as close the antenna feed point as possible. The cable from the radio to the tuner is COAX, and is therefore shielded already. Once the wire leaves the tuner, it is simply #10 wire with an extra heavy insulation coating on it. (NEVER USE COAX AFTER THE ANTENNA TUNER!) You can even get away with #10 wire in a pinch, although GTO wire is nicer as it has slightly more ability to reduce the chances of RF burns if someone grabs the GTO wire while someone is transmitting.
#6> If you have stainless steel lifelines, coated or not, it is a good idea to grab the bottom of one of the stantions in your grounding foil run. Generally I do this at the back of the boat in the cockpit lockers as far aft as possible, and actually connect to the pushpit. This takes a lot of the RF off of the lifelines which can help prevent RF burns should the crew grab the lifelines or pushpit while the radio operator is transmitting.
All this assumes that you have MODERN ELECTRONIC antenna tuner. If you have an old fiddle the capacitor nob, and a rolling inductor, or taped inductor, then you are more than likely going to have to spend a few hundred dollars lining the inside of the hull of your boat with copper foil. Since this is more money that the new tuner will cost you, I would recommend getting a new tuner.
#7> I am open for questions on installs if you want to ask them here.
Guy