Bus Bar for Engine Grounds

Let me make sure I understand how to add a negative bus bar for the engine grounds to get them off the engine block. Maine Sail's instructions are here , under "All Cleaned Up." AS part of this project, I'm also jumping the alternator direct to the starter solenoid per Maine Sail.

Here's my current wiring. You can see several grounds are on rusty quarter inch studs on the block, with corroded wires and the wrong size ring terminals.

So

--Mount a heavy Blue Seas 4-post negative bus bar on the fiberglass engine stringer.

--Run a heavy cable from the alternator stud to the bus bar (using same stud as the new jumper to the starter)

--Run a cable from the starter mounting ear to the bus bar. What gauge wire?

--Relocate the existing 6(?) gauge negative battery cable* from the side of the block to the bus bar.

--Leave as is the heavy duty black cable* from the battery bank to the lower part of the block.

--Relocate the smaller grounds from block to bus bar after re-terminating them with correct ring connectors.

*these cables are hard to see, but have paper stickers on them in the photo .

Questions/Uncertainties are in bold.

Any confirmation or correction appreciated.

For convenience, here is Maine Sail's description (link in previous post):

I have also installed a neg engine bus bar on the engine bed stringer. A neg wire the same size as the alternator positive is connected directly to the alternator and then to the new negative bus bar.

The second wire from the left goes directly to the ear of the starter for the best possible negative return to the battery bank. I don't like running hundreds of amps through a rusty engine, paint, corrosion and multiple dissimilar metals before it can go back to the batteries. This direct wiring to the starter ear creates less voltage drop and makes for a happy starter motor.

The third wire from the left, under the hose, runs directly back to the negative battery post and carries the alternator and starting currents.

Hmm. A good question on main grounding cable from the battery to the block. I had been thinking to run directly from the battery to the new bus, which I believe is as Maine Sail has shown it. Will have to study that a bit more.
Any particular logic behind locating the bus on the stringer? Short wire runs? Perhaps the choice is installation specific.
The stringer would be rather inaccessible on my boat. I'm aiming for the rear bulkhead behind the engine. I have too many wires and hoses going across the engine, and close to rotating parts, since the alternator and pumps are on the opposite side from the devices that they connect to. Currently, most of my grounds are scabbed onto the transmission cover.
All the parts are in a box on the workbench (except I haven't yet acquired a shunt for a new ammeter.) Guess I'd better get at it pretty soon. I still have to sit down and carefully work out a new mains positive arrangement, but I guess that improving the grounds is not dependent on that. Except as they may compete for real estate.

My boat like maine sail pic, so convenient.
Still not clear on ground vs. grounding or if need new return wire from bus.

Christian Williams said:

My boat like maine sail pic, so convenient.
Still not clear on ground vs. grounding or if need new return wire from bus.

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First, there should be only one wire from the battery negative to anywhere on the boat. This is so you can install a battery monitor shunt in the future. On my boat I kept the original 1/0 and used #2 for additions. My house bank is very close to the engine so runs are short.

If you are going to run a wire to the starter you don't need another wire to the block. This wire should also be at least #2. Since every production car and boat ever built uses the block for the starter motor ground I don't think adding the wire is much of a priority. Keep in mind that MS prides himself on doing Rolls Royce caliber work for which he submits a bill. I can't say anything bad about that, but I don't see a need for me to work to that standard. YMMV.

On my boat I added a hunk of copper to the ground point on the engine and use that for the additional grounds such as the start battery, alternator, charger, and windless, etc.

I could make a case for running from the battery to the starter and then from the starter to the bus. That would eliminate some connection points (voltage drops) in the heaviest and most important current path, but would generally be a PITA and would require more wire. I certainly wouldn't recommend it.

BTW that just happens to be on an Ericson 32-3....

The engine "ground" is now the lower ear of the starter motor. I prefer to place engine grounds directly on the starter mount bolt so there is less chance of voltage sag when passing a couple hundred amps of starting current through rust, paint and multiple dissimilar metals to the opposite side of the engine. I also prefer to give the alt the same chance and that is why it also connects to the bus with it own wire.

Only one wire runs back to the battery bank in that photo and it hits a shunt, right next to the bank, before getting there. I am just not a fan or passing large current devices such as an alt or starter through rusty metal, paint and dissimilar poor conducting metals and prefer an all copper pathway when possible.. It was possible on this boat and the parts were pretty cheap to do so.. That boats wiring and engine were a complete nightmare and the owner could not leave the dock for 5 minutes without experiencing some sort of electrical failure.... That alt was also re-built and is now isolated ground so required its own neg path back to the batteries......

All the battery bank wiring, starter, neg, shunt & to batt switch on that boat is all 1/0. IIRC the alt neg and alt + are 2GA.... Depending upon alt output can easily be smaller as they are very short runs.

Christian Williams said:

For convenience, here is Maine Sail's description (link in previous post):

I have also installed a neg engine bus bar on the engine bed stringer. A neg wire the same size as the alternator positive is connected directly to the alternator and then to the new negative bus bar.

The second wire from the left goes directly to the ear of the starter for the best possible negative return to the battery bank. I don't like running hundreds of amps through a rusty engine, paint, corrosion and multiple dissimilar metals before it can go back to the batteries. This direct wiring to the starter ear creates less voltage drop and makes for a happy starter motor.

The third wire from the left, under the hose, runs directly back to the negative battery post and carries the alternator and starting currents.

The fourth wire that can't be seen, behind the hose, goes to the start bank neg....

View attachment 13418

Click to expand...