Hunter 356 Zinc Bonding

JohnSn

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Feb 19, 2011
18
Hunter 356 51111 Dana Point,CA
Hi Folks,
I've been impressed with my 356 and the engineering involved. But, I do have one problem. The thru-hull for the engine water inlet is slowly corroding.

The other thru-hulls are bonded to a submerged zinc mounted in the hull. They show no signs of corrosion. But, the engine water inlet thru-hull is bonded via a long, circuitously running wire to, I believe the lead keel. As I understand the galvanic series, that's not a good way to prevent corrosion on the thru-hull.

I'm considering removing that long circuitous wire and bonding the engine water inlet to the zinc mounted in the hull. But, I'm reluctant to modify what I've seen as a very solid engineering job. How are other's Hunter 356 thru-hulls bonded?

Thanks for the help,
John
 
Mar 20, 2004
1,729
Hunter 356 and 216 Portland, ME
Hi John,
can you post some pictures? I've never seen a 356 where the thru hulls were bonded - they're electrically isolated from the rest of the boat. Also, what/where is there a zinc mounted on the hull? Could this be a PO modification?
 
Jan 30, 2012
1,123
Nor'Sea 27 "Kiwanda" Portland/ Anacortes
Whoa -- this is a very silly arrangement. Lead is the more noble hence the through hull ends up protecting the keel.

To the point - cut (better remove altogether) the cable that presently connects the cooling water intake to the keel. Better the cooling water intake stands alone - no connection to anything else.

In fact get rid of any bonding cable that ends at the keel.

Charles
 
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Mar 20, 2004
1,729
Hunter 356 and 216 Portland, ME
Right, Charles!
The only thing on the 356 that should be bonded to the keel is the mast - part of the lightning protection system
 

JohnSn

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Feb 19, 2011
18
Hunter 356 51111 Dana Point,CA
Thanks so much for the input so far!
It's interesting to hear that not all 356s have this feature! My boat was built in August 2002, S/N 35320. I'm starting to wonder if this feature was only on boats built in a particular timeframe. I doubt this was added on. But, I can contact the service manager who supported the vessel since it's initial delivery.
Here's the pictures. I've added text to the photos to describe what you're seeing.
I'm not certain that the wire I've identified as going to the keel actually goes to the keel. I, as of now, haven't pulled up the floorboard.
IMG_4157.JPG
IMG_4158.JPG
 
Mar 20, 2004
1,729
Hunter 356 and 216 Portland, ME
Thanks, John, that helps.
I still think what you're seeing is an add-on, not a Hunter original setup. First, there is nothing in the 356 manual about this grounding system or the thru-hull zinc, either in the description, drawings, or schematics. Second, note in your pictures that a ground wire runs to the head pickup and then a short wire runs to the zinc - it's a bad practice to not use homeruns to the zinc. Also, the crimps are not glue filled shrink insulation,which would be used in a wet area. I also think that the really heavy gauge wire to the engine thru hull from the keel (?) is a major error and extremely dangerous; if that wire goes to the keel it is effectively connecting the thru hull into the lightning protection system and providing a high current path for lightning to the bronze thru hull - essentially a point path into the water. I would expect a strike to make a very large hole in the bottom of your boat there. I would definitely talk to the service manager and see if he can tell you what's going on.
FYI, Escape is s/n 198, built in April 2002
 

JohnSn

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Feb 19, 2011
18
Hunter 356 51111 Dana Point,CA
Thanks Chuck and Jerry!
And Thanks so much for the picture!
Chuck's vessel was built a few months before mine. Jerry, when was your vessel built? If we can establish that a vessel built after mine also didn't have this feature, then it's a given that this was not provided by the factory during that timeframe.
I'll contact the service manager. Given the date, I don't expect to be able to connect with him for a week.
I'll also pull up the floorboards- the expected wire to the keel must be sorted out right away.
I also need to revisit the wiring that connects the thru-hulls to the zincs and consider replacement.
Merry Christmas!
John
 
Mar 20, 2004
1,729
Hunter 356 and 216 Portland, ME
Merry Christmas, John and Jerry!
My new project before spring launch is to get my bilge as clean as Jerry's!
BTW, Hunter had issues with the original thru hulls (corroding ball shafts) and recalled them for replacement at Hunter's cost. I think the blue handled valves in Jerry's (old?) picture are the bad ones, all of my new valves had the yellow handles
 
Mar 3, 2003
710
Hunter 356 Grand Rivers
Chuck and John: Merry Xmas to you too. Note the date on that photo was 2004! I wish it was still that clean! It isn’t! Chuck is right about the thru hulls. Mine were all replaced and my thru hull handles are yellow now. I’d forgotten about that recall Chuck.

My hull number is 352 . I used to know how to decipher the number, but i’ve Forgotten how. Built as a 2003 model in late 2002 per my documentation. I bought it new around March 1, 2003 from Lighthouse Landing in Grand Rivers, KY on KY lake. It hadn’t been there long when I bought it. I traded my 5 year old 260 in when I bought it. If yours is 353, it was in line when mine was. Somebody other than Hunter put those wires on your thru hulls.
 
Apr 21, 2014
184
Hunter 356 Middle River, MD
John,
My hull # is 298 and was built in July 2002 but is a 2003 model per the Hull ID Number. Our thru hull area is just as clean as Chuck's and we have the six thru hulls present (extra for generator here, another one for wash down in the bow and maserator in the stern) and have no grounding wires present from there, just the large one form the mast post to the keel.
Is there an externally mounted zinc on the hull that that wire attaches to?
One of the many things I like about the 356 is the thru hulls all in one location, as I shut them every time I leave the boat.
Jeff
 
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JohnSn

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Feb 19, 2011
18
Hunter 356 51111 Dana Point,CA
Hi Jeff,
Yes there is a zinc mounted on the hull. The mounting bolt can be seen in my picture. Its roughly midway between the two thru-hulls to port.

All,
Ok, I chased down the wire from the engine raw water inlet thru-hull. It goes to the arch! Now I’m even more confused.

I put in a question to the boat yard. I’ll update here when I get a response.

Does anyone have a wire coming from the arch to some bonding point? On my vessel, the connection to the arch is in the vicinity of the fuel filler nozzle.
Thanks,
John
 
Mar 20, 2004
1,729
Hunter 356 and 216 Portland, ME
nope! only the wiring for the cockpit light and the speakers. I've looked at the mounting bolt areas for my arch and there's nothing there
 

JohnSn

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Feb 19, 2011
18
Hunter 356 51111 Dana Point,CA
Thanks Chuck,
I'm leaning toward thinking that the arch should be bonded to the keel. While the engine raw water inlet thru-hull should be bonded to the zinc. That would give me lightning protection for the arch. And corrosion protection for the final thru-hull. Before I make that change, I'd like to hear that someone else has a boat with the arch bonded to the keel.

I forgot to mention that I also found that the blackwater thru-hull near the transom is also bonded to the in hull zinc.
 
Mar 20, 2004
1,729
Hunter 356 and 216 Portland, ME
John,
According to Hunter, the mast/keel lightning protection system protects the boat in a circle about 1 mast height in radius. this includes the arch. While IMHO lightning protection science is somewhat dubious, I wouldn't ground the arch - I think that would just provide another potential path for the lightning.
Corrosion protection science, on the other hand, is well established - all of the thru hulls are isolated from the rest of the boat's metal and shouldn't need a connection to a sacrificial zinc. I'd disconnect all of those wires unless someone can tell you why they are there.
 
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Mar 3, 2003
710
Hunter 356 Grand Rivers
John: I agree with Chuck. The PO somewhere along the line got some bad advice. If it were my boat, I would take all that out. Two grounds is generally a bad idea as it sets up potential between the two and could make you more likely to get struck by lightning.
 
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JohnSn

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Feb 19, 2011
18
Hunter 356 51111 Dana Point,CA
Regarding grounding the arch, I think that’s good logic. But I’ve been waiting to see if Hunter did that on anyone else’s boat.

My radar and vhf are mounted to a short mast mounted to the arch. I wonder if the ground plane set up by the arch is helpful to signal strength? Anyone else have an arch mounted vhf and radar and bonded arch?
 
Mar 20, 2004
1,729
Hunter 356 and 216 Portland, ME
neither radar nor vhf need a ground plane.... My radar, AIS antenna and second VHF are mounted on a stern mast. Where did they put your radar on the arch? unless you don't have a traveller I'm surprised it fits.
 

JohnSn

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Feb 19, 2011
18
Hunter 356 51111 Dana Point,CA
Chuck,
Radar is mounted to a mast on the arch. To ask again, does anyone have a ground wire connected to the arch? I think I’ll disconnect the wire from the arch and see how the radio range is affected.
C26F7C63-C6D3-482B-8766-F6049ABFDEEE.jpeg