greenwire on fuel tank near sending unit

[pancake]

ok now the plot thickens. i do leave it in salt water in a slip. so it should be attached to engine mounting bolt,( or if you have a threaded drain plug, to one of the screws holding the drain plug housing) . do you mean the brass garboard drain? my brass garboard drain is screwed in from outside the boat with stainless steel wood type screws and 5200 caulk. is that what you are referring to?

not sure where or which engine bolt on the outboard i could attach it to. would you run it out thru the harness to something on the outboard engine?

i'm wondering if this may be a cause for all the corroded aluminum fuel tanks?

[RidgeRunner]

It needs to go to the negative post on the battery as Spare pointed out. But if you have another suitable ground, whatever it may be, you can get away with attaching it to that. The garbord style drain plug you described will not work for this purpose as it is not grounded to the battery. If your battery is in the back just hook it to the negative battery terminal. If you don't have a battery back there you could hook it to one of the four bolts that hold the engine to the transom. I don't like that because you will need a 1/2" eye terminal to go over the bolt and those bolts should be sealed with some sort of caulk/sealer to protect the transom from water intrusion which may prevent you from having a good ground to start with, but it is your call. You could run it to the engine and ground it to the block but the manufacturers just run it directly to the battery and then they are not relying on the guy rigging the engine to make this connection. It is considered part of the boat wiring and unrelated to the engine wiring.
USCG requires aluminum and steel tanks to be grounded and YES it could lead to tank failure from electrolysis.

[pancake]

ok, thats what i will do , negative batterry terminal. this was one of many cut / unused wires on my boat.

[RidgeRunner]

I forgot to welcome you to the board. Pancake, welcome aboard.. We love pictures as someone has probably already said.

With respect to leaving your rig in the drink and tank corrosion, I think salt water will eventually corrode anything. Most tank corrosion I have seen is from lack of proper drainage of water from around the tank. If you have no leaks in the boat the tank should remain relatively dry and that is what you want. If salt water gets to the tank for whatever reason, the ground will help to slow the electrolysis. Also, thru hulls below the water line, like the drain plug, could stand to be grounded which is a real PITA.
I definitely recommend you use at least one sacrificial anode. They are made from some sort of aluminum alloy that is a softer metal, (less noble) than the engine bracket or brass drain plug. Most outboards have one at the bottom of the clamp bracket. The annode will corrode due to electrolysis and give up ions to the other metals instead of the other way around. Replace the annode as necessary or at least once per season. If you do bottom paint don't paint the annodes it renders them useless.

[spareparts]

it should be hooked to the engine bolt, and the gar board plug(run a machine screw thru one of the holes for the plug instead of a wood screw, use a nut on the inside of the hull for the green wire to hook to it), and anything else that touches salt should be connected to green. They tell you the ground bonding wire is a separate circuit than the battery ground, but they usually end up connected at some point. If its hooked to the engine , you shouldn't have to hook it to the battery ground

[SkunkBoat]

Your motor is connected to the battery. The Black wire is connected to the negative terminal. So you can connect the tank ground to the negative terminlal or any place that is also connected to the negative terminal.
Usually the fuel fill and vent have a ground wire too.

As for corrosion of the tank, make sure you seal the hatch with silicone so water doesn't get in. If you remove the foam & tank you'll see that it is in an Undrained compartment. Any salt water that gets in stays there forever. Thats what corrodes tanks.

[pancake]

yes they do have the original wire still connected.