My preferred method for starting battery ground is to run a heavy wire from the battery negative terminal directly to a stud on the starter. Another lighter wire can go from the stud on the starter to the hull itself. All engine functions and anything else powered by the battery should return to the stud on the starter, not directly to the hull.
The first wire must be sized for full starting current, the wire from block to the hull should carry no current at all, but probably it is a good idea to use at least AWG 10.
This is not the way the factory did it. They wired all grounds to a stud on the hull. This has the disadvantage that it is difficult to isolate shorts to the hull if you can't get the grounds isolated from the hull. It also puts another connection in the starter circuit, often a source of trouble. But it is convenient to do, and of course works OK.
Fuel fills and tanks must be grounded to the hull, not to the engine block, per USCG. Check with Jeff, who knows the CG regs.
If you have brass or bronze fittings below the waterline, they should be isolated from the hull and NOT bonded to the hull. Aluminum, brass, and water make a little battery, and if you connect the aluminum and the brass with a wire, current will flow and the aluminum will be consumed. I would go with the DNR guy and not the surveyor on this one. Don't just take my word for it, either....it is too important.
My bronze underwater fittings were isolated by the factory using micarta and are still in good shape. They do NOT have any wires on them, or any place to put one. I think the factory got it right. I wonder if others have the same setup.
1975 32' Flybridge Sedan, twin Perkins 6-354 diesels, 1:1.53 velvetdrives, 16 X 19 props. Merritt Island, Florida
