Hunter 42 Passage Grounding wires in center bilge.

[n0where]

Hello All,

I have a 1994 passage and I am re-doing the binding system, etc.

There are two black wires in the main center bilge that seem like they are fiber-glassed right in and bonded to the keel bolts. They don't come out of any pre-drilled hole,they look like they were slapped in-between some fiberglass layers, then ran to the keel bolts. Anyway, 30years later, these wires are basically completely corroded over time and need replacing. I can not find where they go. Ive tried continuity testing to all kinds of locations on the boat and nothing! Anyway, just wondering if anyone knows where these go.

 

[jssailem]

I was having no luck searching the SBO manuals for an electrical diagram of the Hunter 42 Passage Bonding system.

Here is a ChatGBT summary and image results. Use at your own discretion.

Note:

• Keel bolt bonding is sometimes debated—Hunter Yachts sometimes did not bond the keel, reasoning that it’s immersed anyway and galvanically isolated. However, bonding the keel helps with lightning protection and provides a common reference point for underwater metals.
• If you’re using the keel as a lightning ground, a #6 AWG tinned copper wire is typically used from a lightning dissipater to the keel bolts or a copper grounding plate.
• All underwater metals (thru-hulls, struts, engine block) should be tied to the same bonding system if they are not isolated.
• The AC shore ground is usually connected to the bonding bus bar per ABYC E-11 unless you’re using an isolation transformer or galvanic isolator.

Keel Bonding and Grounding System Diagram Overview

Main Components:

1. Keel bolts (embedded in bilge)
2. Bonding wire (green or green/yellow) – 8 AWG stranded tinned copper (typical)
3. Ground bus bar – usually near DC panel or engine
4. Through-hull fittings (metal only)
5. Engine block
6. Propeller shaft bonding strap
7. Lightning protection if installed
8. DC negative bonding

 

[n0where]

They are distinctly black and not green which are leading me to believe they might be something else and I have other green bonding wires to other bolts. So I'm looking to see if anyone with this boat is familiar with what there wires are. But, Thanks for looking.

 

[Davidasailor26]

If the black wires were properly color coded they’d be either AC hot or DC negative. Neither of those should be connected directly to the keel. My guess is that the wires were either tied into the bonding system or a previous owner’s attempt at who knows what. If they don’t have continuity to the bonding/neutral bus now I’d say they’re not serving any useful purpose, possibly because they’ve corroded and fractured somewhere. I would check that the bonding system is in some way tied to the keel, and there the bonding system is tied to the neutral bus at one point.

 

[American_Mainsail]

Do they have continuity to the chain plates/rigging? My guess is that these are grounding for lightning protection.

 

[Terry Cox]

Anyway, just wondering if anyone knows where these go.

Our boat has keel grounding wires, but nothing like what your picture shows. Sorry.

 

[dlochner]

Look at the mast step and the bolts for the chain plates, as @American_Mainsail said they could be lightning protection. Although given the apparent wire size (10 ga?) they won't last long in a lighting strike.

And I certainly would not trust ChatGPT on a wiring issue on my boat. Bonding and grounding have very different meanings but are often used interchangeably. Bonding refers to connecting all the below water metals together to equalize their galvanic potential to prevent galvanic corrosion. Grounding refers to providing a path for electricity to go back to the source, a poor term for the DC system and there is always current in the DC- grounding wire. In AC systems the ground wire is an alternative path back to the source in the case of a ground fault. Ideally there should never be current on the green ground wire.

 

[n0where]

Do they have continuity to the chain plates/rigging? My guess is that these are grounding for lightning protection.

I tried to check before and nothing, but I realized they might be coated pretty badly, so ill try again.

Our boat has keel grounding wires, but nothing like what your picture shows. Sorry.

Do you happen to know off hand exactly what your grounding setup is or what wires are connected where?

I have two black wires to the keel bolts under the stairs that look factory. I also have the mast post connected to a bolt in the main bilge.

 

[n0where]

Look at the mast step and the bolts for the chain plates, as @American_Mainsail said they could be lightning protection. Although given the apparent wire size (10 ga?) they won't last long in a lighting strike.

And I certainly would not trust ChatGPT on a wiring issue on my boat. Bonding and grounding have very different meanings but are often used interchangeably. Bonding refers to connecting all the below water metals together to equalize their galvanic potential to prevent galvanic corrosion. Grounding refers to providing a path for electricity to go back to the source, a poor term for the DC system and there is always current in the DC- grounding wire. In AC systems the ground wire is an alternative path back to the source in the case of a ground fault. Ideally there should never be current on the green ground wire.

I've been trying to pin down a reason why my zincs are getting decimated. In the process I have been upgrading a lot of my bonding wires to 8 gauge and the mast post to 6 (but most of my thruhulls have been moved to marleon) and checking the system and busses. In trying to find the source of the problem I realized that that two odd black wires in the bilge that were connected to the keel bolts.. were in fact not connected because the end crimp failed. The problem is that since they are wires in a wet bilge, There is significant corrosion and I have to potentially re-wire a significant length beyond where I can access directly to create a clean crimp.

 

[jssailem]

I've been trying to pin down a reason why my zincs are getting decimated.

You are seeing the results of galvanic corrosion. The zinc’s are saving the rest of your boat metals.
If this is happening quickly then where your keeping your boat or the electrical systems in your boat are putting an electrical charge in the water.

Your bonding system is an attempt to put the connected metal parts (ie. Thru-hulls and valves) at the same electrical state. It will not stop the zinc from eroding. If the zinc is gone then the bonded metals will begin to erode together.

You need to address the electrical leak. Bilge pump wires in the water. Submerged wire connections. AC power leaks from the dock. Other boats with electrical shorts nearby.

If you can’t fix the electrical issues at the least keep replacing the zinc’s when they reach 50% corrosion. They are cheaper and easier than thru-hulls, props, and prop shafts.

Consider installing a galvanic isolator or an isolation transformer.

When your boat is plugged into shore power, the green safety ground wire connects your boat’s metal parts (through the bonding system) to every other boat and the marina’s shore ground. This creates an electrical path where small DC voltages can flow and lead to galvanic corrosion — the slow steady deterioration of your underwater metal parts (propellers, shafts, thru-hulls).

 

[dlochner]

I've been trying to pin down a reason why my zincs are getting decimated.

Do you have a galvanic isolator? A prime cause of galvanic corrosion is other boats in the marina when you are connected to shore power.

There is an excellent article on galvanic corrosion in the Summer 2025 issue of Professional Boat Builder magazine by Steve D'Antonio. A subscription to ProBoatbuilder is free. Worth subscribing and reading the article.

Professional BoatBuilder: An IBEX Technical Journal - Written for boatbuilders, repairers, designers, and surveyors

www.proboat.com

 

[Terry Cox]

Do you happen to know off hand exactly what your grounding setup is or what wires are connected where?

Sort of. A grounding wire connects to the forward most keel bolt and another connects to the shaft log. A galvanic isolator in located behind the nav station power panel. Each year I install two light prop shaft zincs that last a year, with very little material left.

 

[n0where]

Yes, we have a galvanic isolator and Ive tested it.

What I am noticing is that when I connect one end of the multimeter to the black wires and the other to the keel and test for voltage. There is a voltage differential of up to.5v when I turn on certain electric circuits. So there is for sure some kind of voltage differential going on there.

 

[n0where]

Sort of. A grounding wire connects to the forward most keel bolt and another connects to the shaft log. A galvanic isolator in located behind the nav station power panel. Each year I install two light prop shaft zincs that last a year, with very little material left.

OK, I think thats what I have there also. Bu there are two wires. So maybe one is to ground and the other is to the shaft log. I'll have to try and trace those two down.