Bonding & Grounding

[grady]

I am in the process of completing my complete rewire. I was wondering if bonding my two gas tank together and tying them into my grounding circuits. ( basiclly -12v )

They are Isolalated in seperate compartment, and only have rubber hoses for connections (although the fuel fill has wire reinforcements)

My stainless fuel fill deck mounts have to be bonded but do I bring them into the ground (-12v) circuit and if I do should I bond the tanks with them.

I'am concerned with stray current. I don't have a external dynaplate bonding system.

I do have a single metal below the water line thru hull.

anyway please advise as to the best way approach this task.

P.S. I really didn't want to take on the expense of a seperate bonding system.

Thanks Tony.

[CDK]

Bond anything you don't want to have on a higher potential than the water around you. The tanks, the engine(s), the filler plumbing and ultimately some metal surface in the water. That is your "ground".
Connect it to the negative terminals of your batteries, but do NOT connect it to anything on the shore because nobody can guarantee you that their ground is the same as yours.
If your metal object below the waterline can be eaten away by electrolysis, protect it with a large piece of zinc.

[pamarine]

I am a bit unclear on what you are referring to as your "grounding system."

Are you referring to an AC ground or your DC negative circuit?

[gonzo]

You are required to bond your tanks to ground. The shaft and propeller should provide some grounding.

[baeckmo]

CDK's answer covers what to do. In addition, if you use a charger from shore, make shure its trafo has primary and secondary windings completely separated. Some cheap crap comes with one end in common, which will let any floating ground potential from shore net into your system, causing corrosion.