Adding a large ground wire, WHERE???

[Flux]

I want to add a nice double bus under my dash for adding future amps and custom ballast. I have taken a good look at all the electrical, especially the battery cables. My boat is an 02 SANTE. It seems that the only power available under the dash is off the black box, which has the pos and neg terminals and several light gauge wires on them. I assume that it takes it's power from the 10 ga wire on the dual battery switches. I don't want to tax this system and prefer to set up my own buses with large gauges from the battery switch and a ground from the engine. I figure wire gauges for 100 amps will be fine (2 gauge) and I doubt it will see that much but better to oversize and do it once.

I have located what I think are two grounding studs on either side of the engine and one on the aluminum engine mounts. The one I am considering is located beneath FCC, it has the rear battery ground on it as well as several other smaller gauges. The front battery ground runs through the bow and into the hole below the dash and on to the aluminum frame that holds the engine where it is bolted down.

I am also considering just splicing the front battery ground and attaching it to a new bus bar , this would be easiest but I don't know if it might over-amp that wire, it's 2/0 but runs the length of the boat. The shortest route other than the splice would be to attach the new ground on the front battery, but that again taxes the front battery ground.

So I think I should either ground to the engine ground under the FCC or ground to the stud on the aluminum motor frame. Any thoughts on this?? I know this is lengthy but I don't want to cause any damage to the existing system and this is the safest way I can think to do it. Is the aluminum frame as good a ground as the engine ground??

I will take my pos power right from the battery switch studs.

[01superair]

Flux - If Grant doesn't reply to this give Clay a call at the shop, he has done a ton of wiring on Super Air's and he would be the one to talk to on this.
650-622-9229

[Flux]

Thanks Superair. I would actually feel a little strange about doing that honestly, mostly out of respect for them and their business. I wish I had the coin and was local to them, there is nobody I would rather have messing around with my boat. When Grant chimes in on posts I feel lucky, the dude has shared alot alot of knowledge with folks and his wisdom from countless hours spent in cramped spaces making boats better.

As best as I can figure it, I can ground from either the engine grounds or the aluminum frame, they are all tied together so things should be just fine either way. I can always swap from the aluminum frame on the deck and to the engine if i run into any ground loop trouble from future amps.

My biggest issue really is the power under the dash. There is one wire coming into the black box for each pos and neg, they used those terminals to tap for the small stock amp and the automatic bilge. Everything electrical is tied into that black box, which I am sure is just a box full of relays and breakers. While it is nice and clean as far as where the breakers are, it can only handle about 30 amps total from the fuse that is on it's power line from the battery switches. It just gives you limited options. With all three pumps going and the stereo on, it could easily pull that much.

So my little ballast project turns into a medium size one. I am adding a blue sea dualbus plus bar under the dash and some nice heavy gauge wire feeding it. This way I have good place to tie in another 100 amps if I so desire. It is also seperate from the stock electrical which I am sure I could overtax without any issues. It will draw power from the battery switch lugs and bypass the boats ignition stuff, which has it's pros and cons, I just don't know how big their relays are. One thing I am sure of is that they minimized their wire gauges and left no room for upgrades, which is why I am forced to install my own power lines.

Thanks for the reply and the info, I will document what I did and if it works I will post the process.