Marine Wiring Question: Common Ground attached to the Aluminum Hull?????

[Drewski Canuck]

I bought a Surplus RCMP Boat which had most of the equipment removed. The boat was used in fresh water only, and is really low hours.

I took off a Lowrance LMS480 Sounder and GSP Pod, and noted the power connections which seemed very normal, but with a BUSS glass fuse holder in line.
On the Boat there is a Positive sub panel which has toggle style switches, that I have never seen before. These switches are not fused. A number of ATS Fuse Holders are attached to leads going out from the switch panel.
On closer inspection, I saw that there was a grounding block which is attached to aluminum angle which is bolted to a firewall welded to ... The Aluminum Hull????

Using a Chassis ground on a truck or car is common but I have never seen an aluminum boat hull with a Chassis ground. On my prior boats, the ground was always isolated from the hull, which protects from stray voltage in salt water. I have extensively rewired to get away from the dash "pop" fuses" and I expect I will have to do this all again!

I am inclined to pull off all this common ground and isolate the Ground block from the Hull with a Sea Sense Isolated Ground Rail. Would anyone with more experience be able to guide me if I am fretting over nothing?

This boat is a 19 foot welded Aluminum which I plan to keep and have alot of electrical to add on. I have always battled corrosion on wiring in a salt water environment. I'd like to do the best job possible the first time! Any help would be appreciated!

Drewski

 

[zurk]

hulls should never be a ground. pull it all and your common ground is battery negative.
get a couple of blue seas dualbus bars, take everything off and do it properly.

 

[sudsy]

Its not uncommon for aluminum hulls to have one single bonding wire from the negative battery terminal mounted directly to the hull.

As soon as you mount an outboard motor to your aluminum hull and connect the positive and negative wire to yoir batteries you are bonding your negative bus to your hull.

If that bond is not perfect (any resistance) your have a resistance potential difference and can cause stray current and subsequently corrosion.

Adding a bonding wire is common practice by ABYC standards. Never use your hull as a return path for wired systems in your boat, always positive to positive bus, negative to negative bus. There is a lot of information online about bonding on aluminum boats.