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Author Topic:   Grounding Electrode on Transom

c_mccann posted 07-14-2009 03:39 PM ET (US)
I removed the round bonding and grounding electrode on the transom of my Revenge 25 last weekend. A few observations:
It appears to have been eaten away in time. It was secured with one screw in the center that was not sealed to the hull, and there was another unsealed hole to accommodate the nut that attaches the bonding wire to the bonding electrode.
Why is Whaler punching holes in their transoms below the waterline and not sealing them?
Does the bonding or grounding electrode get eroded in time? The bonding electrode on my boat is small now, barely 1/4-inch thick and tapered.
Who has new bonding electrodes of this same size and composition?
The bonding electrode on my boat had antifoul paint over it. Should the bonding electrode be left unpainted?
I have to let the transom dry out for a few weeks and then seal the holes. The wood was wet, not rotted. I was going to over drill the holes and let it dry out and repair the glass and gelcoat.
Any insight is appreciated..
jimh posted 07-14-2009 06:34 PM ET (US)
The small circular grounding anode seen on the transom of many Boston Whaler boats is made from bronze, I believe. Bronze is a more noble metal than the zinc or magnesium of sacrificial anodes or the aluminum of most outboard motors. If there is galvanic corrosion those less noble metals should be wearing away before the bronze grounding anode. If you are seeing corrosion of the bronze, you have some serious galvanic corrosion going on.
The purpose of the small circular grounding anode is to establish electrical contact with the sea. Covering it with paint will inhibit electrical contact. Do not cover the bonding anode with anything.
I do not know of a source for an exact replacement of the small circular bronze anode about the size of a silver dollar. You could use a silver dollar.
jimh posted 07-14-2009 07:25 PM ET (US)
Based on my own experience in disassembly of various parts of Boston Whaler boats, it appears that a sealant or bedding compound for screw fasteners was seldom employed. Most of the components that I have taken apart have been from above the waterline, so I am surprised to learn that something mounted below the waterline was left unsealed.
RevengeFamily posted 07-15-2009 08:40 AM ET (US)
The bronze ground plate if left unpainted will with time slowly corrode away do to the fact it's surrounded by bottom paint.
jimh is correct, never cover the bronze ground plate with anything. If it is covered with bottom paint, clean it off. With time the bronze will become brittle. I removed the one on my 22 Revenge W/T to remove the bottom paint the previous owner had so generously slathered on it. The screw hole was not sealed on mine either. During the re-installation of the disc, I realized how fragile it had become. I am still in search of a replacement.
The sintered bronze disc is supposed to be equivelent to about 6 square inches of bronze plating. (which is what the marine industry use to use for grounding) The silver dollar is a great idea in a pinch, but it does not have the surface area that the disc is suppose to have.
If someone can locate new discs please let us know.
Norm
c_mccann posted 07-15-2009 12:37 PM ET (US)
They are made by Tempo. Tempo is out of business so they are gonna be tough to find. I am going to fix the wet spot, fix the glass and re-mount the old one, I'll find a way to make it work. I am going to glass in a stainless threaded insert in the transom in a glassed hole.. No more water in the transom. I soaked the unit in stripper to get her clean and will go from there.
jimh posted 07-15-2009 09:00 PM ET (US)
All of these notices that the fasteners used with the bronze bonding disc on the transom intrude into the transom with no sealant have prompted me to plan an inspection of my boat for this problem. Thank you for the notice.
ronniet posted 07-16-2009 01:47 PM ET (US)
Could there is a reason for this? I too have no sealant on my anode ,oddly enough on my Revenge and my Bayliner!

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Author	Topic: Grounding Electrode on Transom
c_mccann	posted 07-14-2009 03:39 PM ET (US) I removed the round bonding and grounding electrode on the transom of my Revenge 25 last weekend. A few observations: It appears to have been eaten away in time. It was secured with one screw in the center that was not sealed to the hull, and there was another unsealed hole to accommodate the nut that attaches the bonding wire to the bonding electrode. Why is Whaler punching holes in their transoms below the waterline and not sealing them? Does the bonding or grounding electrode get eroded in time? The bonding electrode on my boat is small now, barely 1/4-inch thick and tapered. Who has new bonding electrodes of this same size and composition? The bonding electrode on my boat had antifoul paint over it. Should the bonding electrode be left unpainted? I have to let the transom dry out for a few weeks and then seal the holes. The wood was wet, not rotted. I was going to over drill the holes and let it dry out and repair the glass and gelcoat. Any insight is appreciated..
jimh	posted 07-14-2009 06:34 PM ET (US) The small circular grounding anode seen on the transom of many Boston Whaler boats is made from bronze, I believe. Bronze is a more noble metal than the zinc or magnesium of sacrificial anodes or the aluminum of most outboard motors. If there is galvanic corrosion those less noble metals should be wearing away before the bronze grounding anode. If you are seeing corrosion of the bronze, you have some serious galvanic corrosion going on. The purpose of the small circular grounding anode is to establish electrical contact with the sea. Covering it with paint will inhibit electrical contact. Do not cover the bonding anode with anything. I do not know of a source for an exact replacement of the small circular bronze anode about the size of a silver dollar. You could use a silver dollar.
jimh	posted 07-14-2009 07:25 PM ET (US) Based on my own experience in disassembly of various parts of Boston Whaler boats, it appears that a sealant or bedding compound for screw fasteners was seldom employed. Most of the components that I have taken apart have been from above the waterline, so I am surprised to learn that something mounted below the waterline was left unsealed.
RevengeFamily	posted 07-15-2009 08:40 AM ET (US) The bronze ground plate if left unpainted will with time slowly corrode away do to the fact it's surrounded by bottom paint. jimh is correct, never cover the bronze ground plate with anything. If it is covered with bottom paint, clean it off. With time the bronze will become brittle. I removed the one on my 22 Revenge W/T to remove the bottom paint the previous owner had so generously slathered on it. The screw hole was not sealed on mine either. During the re-installation of the disc, I realized how fragile it had become. I am still in search of a replacement. The sintered bronze disc is supposed to be equivelent to about 6 square inches of bronze plating. (which is what the marine industry use to use for grounding) The silver dollar is a great idea in a pinch, but it does not have the surface area that the disc is suppose to have. If someone can locate new discs please let us know. Norm
c_mccann	posted 07-15-2009 12:37 PM ET (US) They are made by Tempo. Tempo is out of business so they are gonna be tough to find. I am going to fix the wet spot, fix the glass and re-mount the old one, I'll find a way to make it work. I am going to glass in a stainless threaded insert in the transom in a glassed hole.. No more water in the transom. I soaked the unit in stripper to get her clean and will go from there.
jimh	posted 07-15-2009 09:00 PM ET (US) All of these notices that the fasteners used with the bronze bonding disc on the transom intrude into the transom with no sealant have prompted me to plan an inspection of my boat for this problem. Thank you for the notice.
ronniet	posted 07-16-2009 01:47 PM ET (US) Could there is a reason for this? I too have no sealant on my anode ,oddly enough on my Revenge and my Bayliner!