# Marelon vs. Bronze



## TSOJOURNER (Dec 16, 1999)

I am in the process of replacing all thru hulls on my Irwin 28. Would the marelon be better to use beneath the waterline? Can I use bronze valves with marelon thru hulls? I greatly appreciate any feedback.


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## thomasstone (Dec 21, 2001)

I just did the same thing. I never got an answer I was comfortable with so I used a bronze thru hull for my raw water intake with a bronze seacock( the bronze seacock was cheaper also). That is my only hole below the waterline and I felt more comfortable with the bronze than the marelon.On all of my cockpit drains/deck drains total of 8 I used the marelon drains these are all well above the water line and the marelon are cheaper than bronze as thru-hulls. 
thomas


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## thomasstone (Dec 21, 2001)

oh yeah I probally went the extra mile ,but my exhaust thru-hull is bronze also with a sea cock on it as well, that I turn off once I am out to sea on an extended passage.For regular day sailing I leave it open all the time. I do have a nice bend in my exhaust with a proper siphon break ,but when iwas putting in my engine I met an old salty who ruined his motor from water siphoning in . I figured I would double protect myself. 
thomas


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## Jeff_H (Feb 26, 2000)

I just sold a boat that had Marelon seacocks and through hulls and replaced it with a boat of virtually the same age with bronze seacocks. The Marelon still worked well and required minimal maintenance. Quite a few of the Bronze thru hulls and seacocks are shot and in need of replacement. For a 28 footer I would not hesitate to use the Marelon. 

Jeff


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## TSOJOURNER (Dec 16, 1999)

Another consideration is what happens to the bronze thru hulls if the boat gets hit by lightning??

I''ve heard of metal thru hull fittings disintigrating from a strong lightning strike, as they provide a good path to the water. 

If you weren''t on the boat if this happened, it could sink.

I suppose that and corrosion are the only real disadvantages to using bronze. Make sure the bronze is electrically connected to a sacraficial zinc and that should solve the corrocion problem.


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## thomasstone (Dec 21, 2001)

Would you feel comfortable using a marelon sea-cock below the water? Also its probally alot easier to change down the road since they are impervious to corrsion.If you did use all bronze should you ground them all together ? I noticed when I was fighting to remove old sea-cocks thier appeared to be some sort of wire glassed in, I am assuming this was some sort of ground? I have heard very different opinons on this.
thomas


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## TSOJOURNER (Dec 16, 1999)

I don''t feel uncomfortable using marelon below the waterline, should I? It seems that the marelon is up to the task. Corrosion free sounds good. The most economical way would be to use marelon thru hulls with bronze ball valves. Does this sound like a possibility?


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## thomasstone (Dec 21, 2001)

I dont know, Im asking too. Either way you go I dont think trying to save a dollar in this situation is the way to go. For me holding the bronze sea-cock and marelon in my hand i felt the bronze was more solid. A marelon sea-cock could be superior, maybe some one will let us know?
thomas


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## TSOJOURNER (Dec 16, 1999)

i believe hinkley uses marelon seacocks ant through hulls.
eric


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## [email protected] (Mar 1, 2000)

Hi Mohican,

Is your thrugh hull near the waterlin?. If you carry, marelon and get stucked on your thrugh hull, probably it couldn`t cope with your vessel´s weight. Moreover, heat melts marelon.

In any case, mu boat carried marelon for the last 8 years, and there were OK. I just changed them, because I thought there were old enough. 

Mixing Marelon and bronze spherical valves is not recommende since both materials have disimilar rates of dilatation. However if you will only navigate in waters where it tempersature have a small amplitude, this will not be an issue.

Last, some guys recommend kicking your thru hull and valve after instalation with a ski boot. If it remains in place, means that it was ok. 

Regards
Fernando


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## TSOJOURNER (Dec 16, 1999)

Does it have to be a ski boot??


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## TSOJOURNER (Dec 16, 1999)

I had just one Marelon sea cock that was just 3 years old when, in the course of manipulating the handle to keep the unit working, freely, the handle broke off in my hand. No more Marelon for me.


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## Constantin (Dec 16, 2000)

Marelon has a lot going for it. After all, it will not seize as readily as bronze sea-cocks, is usually cheaper, and doesn''t require grounding like bronze. If you''re not planning on doing a lot of maintenance, it may be the better option. Lastly, Marelon is not attacked by some substances like blackwater waste the same way as Bronze. Furthermore, it doesn''t interact galvanically if you were to attach it to a stainless tank.

Bronze sea-cocks are usually more solid and tougher than their marelon cousins. Reinforced plastic only goes so far. But "Marelon" is not only a brand name, it also assures some modicum of quality. The same cannot be said for a lot of "bronze" fittings which the layperson cannot distinguish from those actually fit for ocean service. Good Alloys cost money, and much of the stuff sold in discount stores is simply adapted from home use and sourced from the cheapest supplier they could find. Caveat Emptor!

Furthermore, bronze sea-cocks require monthly openenings and closings or they will seize hard and fast. Ideally, they should be taken apart and regreased yearly. That keeps corrosion to a minimum. In this sense, the bronze sea-cocks are no different from your average folding propeller which also usually needs a yearly greasing, cleaning, excercise, etc.

Having worked on the entire sanitation system in our boat, I see a role for both systems. Our stainless holding tank had no proper nipples to interface with hose - just a flat tube weldment which leaked invariably. A Marelon fitting might have been more appropriate because it has the barbs that keep the waste where it belongs. On the other hand, that presupposes access to the interior of the tank, etc.

I prefer bronze systems all around, but I''ve also had to deal with seized sea-cocks. They are no fun. One more reason to create a monthly/annual check-list for preventative maintenance. You either do it now or pay for it later. If interested, have a look at www.vonwentzel.net/Prout/ for more info on what we did to make our holding tank system work.


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## TSOJOURNER (Dec 16, 1999)

thinredmohican,
I for one have never been sure about using marelon through hulls below the 
waterline, but here''s what I think:
I picture hitting something like a rock (or that 12''" by 12''" by about 10'' long piece of wood that was floating in the water the other night) I would imagine objects like these would seriously damage marelon so, I, personaly don''t use or recomend them below the waterline.

Dennis L.


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## ndsailor (May 17, 2001)

I would imagine hitting something like that would damage your hull, much less the thru hulls. I think the marelon thruhulls are just as strong as the fiberglass surrounding them and the seacocks only weakness is the handle. If there is fire aboard, well, a lot of fiberglass is going to melt too, probably long before the thru hulls and seacocks melt.


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## TSOJOURNER (Dec 16, 1999)

Hi Rick,
No I don''t think it would damage my hull.
When I passed the peice of wood it was lined up longitudally(spelling?) with the boat. If I''d have hit it like that, it might have slid along the under body in that position and hit a protruding through hull, it would tend to try to shear it off, Do you know if marelon is stronger than bronze? I really don''t know.

Dennis


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## ndsailor (May 17, 2001)

Goood question! I really don''t know. I wonder of any tests have been done regarding how much each would give before cracking. I would assume that the bronze, being a soft metal, would be less affected by cold water where the marlon would (I expect) be more susceptable to cracking if struck by a hard object. In warmer waters I don''t think it would make much difference.....just my feeling on the subject...an easy test would be to take a discarded bronze thru-hull and marlon thru-hull and squeeze both in a vise....waddaya think....Rick


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## Constantin (Dec 16, 2000)

Fundamentally, the bronze units should be stronger and tougher than the Marelon ones. furthermore, they are usually more tapered (don''t need as much thickness for the same strength), so stuff is much less likely to catch on a protuding lip. However, once again it depends on the configuration, the type of impact, and the alloy used. Some are tougher than others.

If the bronze thru-hull is not properly bedded, the first thing to go is probably the hull around it. Any cantilevering action will exploit the 3x lower strength of the hull around the hole. Marelon would probably fail first. Either way, you have a leak to tend to.

Such a failure modes seems somewhat remote. I''d worry more about large logs hitting the bow/keel sections and causing damage the old fashioned way than shearing at the thru-hulls. 

However, it hasn''t reduced my interest in common-box systems where one thru-hull/strainer feeds raw water for the whole boat much like a busbar feeds circuits on the electrical side. This minimizes thru-hulls, the associated maintenance, etc. but requires longer hose runs inside the boat.


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## Jeff_H (Feb 26, 2000)

I am not sure that the Bronze thru hulls really are all that much stronger than Marelon. While the properties of bronze are superior as a material [most bronze through hulls are cast Bronze, (Tensile strength 40-48 KSI)compared to Marelon which is glass reinforced nylon (27-33KSI)] Marelon Fittings are supposed to have heavier wall thicknesses so that they have the equivelient strength in bending and sheer. Marelon is however more flexible and so ''feels'' weaker.

I think the real choice is maintainability. Traditional bronze seacocks take more work to maintain, but no matter where in the world you happen to be, they can be maintained. It is relatively easy to plug the outside of the thru-hull and remove the tapered plug for maintenance. Most Marelon fittings are either not designed for disassembly or count on proprietary parts. Which is why I generally recommend marelon for coastal stuff and bronze if you going distance voyaging. While true marine bronze ball valves are a real favorite of mine and are really best in terms of operation, they lack the easily rebuildable qualities of a traditional tapered plug seacock. There are some neat (compact and easy to operate without freezing up) SS ball valves out there that are used in Europe but I have mixed feelings about those as I have one that is not sealing when closed and which I will replace at next haul out with a bronze ball valve.


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## Constantin (Dec 16, 2000)

The one thing to consider with cast Bronze versus glass-fiber reinforced plastic is that cast Bronze has isotropic material strength while reinforced plastic does not. 

That is, a cube of Bronze has the same strength in all directions, while a cube of Marelon should have higher tensile strength in the direction of fiber flow (while approximately having the tensile strength of the underlying resin in directions perpendicular to the flow of fibers). 

Marelons compression strength is probably not enhanced that much by having glassfibers in the mix. The fiber flow profile would mimic the grain flow inside a forged part. The only difference is that fibers flow from where the injection occurs - this may or may not be in line with needs. I assume that the makers of Marelon fittings have this part figured out.

With proper design, Marelon is every bit as strong as Bronze - just add some thickness to make up for the lower strength and toughness. However, like any material that has unequal material qualities, reinforced plastics require careful engineering.


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## tsenator (Nov 6, 2000)

From the Forespar Web site: http://www.forespar.com/resources/tips/MarelonGen.htm
Marelon® - Marine Grade Plumbing Systems
Non-Corrosive 
Non-Conductive 
Fire Resistant 
Impact Resistant 
Temp. Range -40° to +250° F 
U.V. Resistant 

Critical Marelon® plumbing components are U.L. marine listed (MQ1151R) and exceed A.B.Y.C. (H-27) (American Boat & Yacht Council) standards.

For what its worth --


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## wumhenry (Mar 29, 2006)

I broke the handle on a Marelon seacock in a '94 Marshall 22 last week when I tried to turn it. Didn't put all that much force on it, either. AFAIK, that's not a problem for bronze seacocks.


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## tommays (Sep 9, 2008)

Well

I broke a handle on marine UL bronze seacock BUT i still like metal better I just went with a better seacock


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## Woodvet (May 5, 2012)

The plastics of yesteryear were rarely fiber re-enforced and often inferior. Now they are all over the place in reliability but I feel Marelon is great stuff. 
Lightening is not predictable and makes for a nervous voyage. 
Bronze seacockadoodle-doos (playing with the spell check here)... Will melt from lightening and it most certainly does happen. 
When it does there's no way to say what and if, but if the electronics are down and you are going down as well.... 
I think you see the point. In an instant the heat may open a huge hole where you once had some valuable scrap. 
it would be wise to think of Marelon in the boatyard rather than including it in your epitaph.... 
Of course "there's not a horse that can't be rode or a cowboy that can't be throwed" so we should leave this up to opinion. 
If I could afford it I want all thru hulls in plastic. Metal on a boat should be avoided when possible. 
Bronzes have galvanic action and of course the weight are contributing factors but mostly it's because "lightening is frightening."


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## capt jgwinks (Sep 24, 2013)

As for mixing plastic and metal fittings, I was always taught not to do that on any kind of plumbing. Either metal or plastic all the way. Seems the metal threads can cut the plastic ones if they're screwed together. 
One thing I noticed with the Marelon fittings in my boat: The tail piece where the hose attaches is thicker and has a smaller inside diameter than a bronze one would be. That reduces the flow a little, and on the galley sink drain causes more of a step for debris to get caught on. The Marelon drain clogs up more than the bronze one did.


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## MarkofSeaLife (Nov 7, 2010)

I know this thread is from 2002...
But why would anyone spend such a huge amount of money on an old 28 footer?
Marelon is 4 or 5 times more expensive than regular fittings.
I just did 14 through hills and if they were Marelon the value would be about 2 Irwin 28s a Bavaria plus half a Ford truck tossed in.
Don't over capatilise a boat!


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## Woodvet (May 5, 2012)

A boat is like your true love!
Who buys their true love a Piece of plastic...  

It's not about bestowing riches on the boat. It's about your LIFE and safety!!! 
OF course there are skeptics but when you have a lightening they have the heavier underwear...


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## miatapaul (Dec 15, 2006)

MarkofSeaLife said:


> I know this thread is from 2002...
> But why would anyone spend such a huge amount of money on an old 28 footer?
> Marelon is 4 or 5 times more expensive than regular fittings.
> I just did 14 through hills and if they were Marelon the value would be about 2 Irwin 28s a Bavaria plus half a Ford truck tossed in.
> Don't over capatilise a boat!


What did you use that is less expensive than Marelon? It is certianlly much cheaper than Bronze.


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## Woodvet (May 5, 2012)

For info on this subject of metal vs Marelon you might check out what surveyor in England said with with very informative pictures. 
This who don't have surveys or care need not start here. 
Ignorance is bliss. 
But for those who maintain a level of vigilance over their boat so as not to pull someone else into distress saving their transom... 
Have a gander...
http://www.paulstevenssurveys.com/upload/Seacocks.pdf


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## tommays (Sep 9, 2008)

I will stick with a PROPER MARINE BRONZE USA MADE unit like the groco bv 750 i used in the refit


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## boatpoker (Jul 21, 2008)

Woodvet said:


> For info on this subject of metal vs Marelon you might check out what surveyor in England said with with very informative pictures.
> This who don't have surveys or care need not start here.
> Ignorance is bliss.
> But for those who maintain a level of vigilance over their boat so as not to pull someone else into distress saving their transom...
> ...


Paul is talking about brass ball valves found on french boats not bronze !


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## Woodvet (May 5, 2012)

Copper may be best but over all the bureaucrats are closing in on it. 
The coopers oxide in paint, copper fuel lines and so on. 
"Admiralty bronze" AKA "Silicon bronze "Red bronze" (above water line "Naval Bronze" can be employed). I love the sight of copper in all it's states of decay. After all I spent decades as a copper plate engraver in intaglio etching. When you look at vinegar and urine as mordants you find it is not at at all impervious. 
Thanks for the picture. It is a pretty sight but metal in general is undesired unless it pertains to tradition. 
Back to the practicality though, the advantages of plastic are superior it you're not a bull in china shop. 
Yet Bronze is malleable and bends easy, though it rarely breaks. 
Boats are made of many different solutions. 
I once owned a boat if you scrapped her out it would be as much weight as a person. 
Many will say it is prettier and vanity may be a consideration but not on my vessel When my metal can be put ashore it will be... 
I want to sail....
"This is an alloy that can cover both brass and bronze (red silicon brasses and red silicon bronzes). They typically contain 20% zinc and 6% silicon. Red brass has high strength and corrosion resistance and is commonly used for valve stems. Red bronze is very similar but it has lower concentrations of zinc. It is commonly used in the manufacturing of pump and valve components." 
I am told that it is a little stinger than copper but it's saving grace is it's adaptability to sea water.


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## boatpoker (Jul 21, 2008)

Woodvet said:


> "Admiralty bronze" AKA "Silicon bronze "Red bronze" (above water line "Naval Bronze" can be employed).


Your information is incorrect.......

Admiralty bronze is near 30% zinc and is not suitable for below the waterline use.

Silicone bronze is not "AKA" admiralty as there is only a few percentage points of zinc.

We all know what happens to zinc in salt water.


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## Maine Sail (Jan 6, 2003)

boatpoker said:


> Your information is incorrect.......
> 
> Admiralty bronze is near 30% zinc and is not suitable for below the waterline use.
> 
> ...


In the US _85-5-5-5_ or Eighty-five - three-five bronze is what is used for seacocks by brands such as Buck, Apollo/Conbraco, Spartan & Groco... I have some 70 year old Wilcox 85-5-5-5 seacocks in my barn that came out of a wood boat restoration. Cleaned up they are not discernible from new. Good bronze is pretty bullet proof stuff. High zinc brass with no tin......:eek


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## Skipper Jer (Aug 26, 2008)

Yes I know the thread is a few years old. 

So what does the insurance companies and surveyors say about Marelon thru hulls below the water line?


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## boatpoker (Jul 21, 2008)

Skipper Jer said:


> Yes I know the thread is a few years old.
> 
> So what does the insurance companies and surveyors say about Marelon thru hulls below the water line?


Very few underwriters actually read or understand if they do read the surveys. Most flip to the valuation page and write a policy.

Seacocks as per ABYC are supposed to withstand a 500lb lateral force (paraphrased). I used to put my foot on the valve and apply some pressure to see if it was solid (on land of course). I stopped doing it with Marelon valves years ago ........ I learned the hard way


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## FreeAgent (Apr 19, 2017)

Seems that early Marelon seacocks didn't meet the ABYC standards when they were changed in 89/91. They redesigned the seacocks and they do now meet the standards including the 500lb load on the tailpipe.

Marelon history from Forespar:


> *Standards*
> Around 1987, the A.B.Y.C. established a set of "standards" for recreational watercraft that included guidelines for plumbing components. This was the early stage of the H-27 "Recommended practices and standards covering seacocks, thru-hull fittings, and drain plugs." By 1989 this was published by the A.B.Y.C. and builders were encouraged to comply. By 1991 the Marine U.L. began incorporating the A.B.Y.C. standards into their standards. The biggest change from the original U.L. standard was the A.B.Y.C. addition of a 500 lb. load test applied to the "outermost fitting" (the tailpipe) of the valve "system". This was the first time a seacock was viewed as a "system" including the thru-hull and tailpipe (or 90 deg. elbow) for hose attachment.
> Up until that time, the MF 849 style flanged seacocks were the only style Marelon® valves approved by the U.L. We sold many of these units to Catalina Yachts as well as T.P.I., Hinckley, C. & C. and a host of other prominent production sailboat builders. These units are still sold today, although they no longer have U.L. approval. The MF 849 ½", ¾" and 1-1/2" style valves and the MF 850 1" through 2" style valves would still pass the current U.L. test if submitted. We let the U.L. approval drop when the new "93" series integrated plumbing systems were introduced. Forespar® had to design a new system that would meet and exceed the "new" U.L. standard as recommended by the A.B.Y.C.
> In early 1992, Forespar® undertook the challenge of redesigning marine plumbing in our Marelon® material to meet these new guidelines. This required a tremendous amount of resources as a complete "system" had to be designed, tooled and molded to meet the increasing demand for Marelon® plumbing. This was the beginnings of what we now generally call our "93" series of integrated plumbing systems. The tooling was completed, parts molded and sent to the U.L. for approvals in late 1992. By the spring of 1993, we showed this system in our catalog and we began shipping parts to Catalina Yachts as well as Sea Ray Boats and a very large number of production builders. They have grown in acceptance with production and custom builders every year since then.
> ...


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## mitiempo (Sep 19, 2008)

And then along came Trudesign from New Zealand with a different approach that also meets ABYC standards. Their valves are better built than the Forespar ones are as well.

Marine | TRUDESIGN


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## FreeAgent (Apr 19, 2017)

mitiempo said:


> And then along came Trudesign from New Zealand with a different approach that also meets ABYC standards. Their valves are better built than the Forespar ones are as well.
> 
> Marine | TRUDESIGN


Good find! Did a search to see if they were sold in NA, and it seems Raritan have the exclusive distribution rights for USA.

This link gives good technical info.

This link gives pricing (Seem competitive considering it whole assembly?)


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## RichH (Jul 10, 2000)

Marlon and other 'plastic' seacock valves have vastly improved over the years. Originally they were made of 'modified' nylon 'filled' with fiberglass etc. for 'strength'. 
The problem with nylon years ago was its natural ability to 'uptake' water (to about ~16%), the water within the polymer structure lead to hydrolysis (similar to rusting of metals) of the nylon.
With the advent and development of DuPont ZYTEL® (family) most of the hydrolysis issues have been solved and apparently more 'fiberglass' for strength is now used in the 'mix'. 
A few years ago I would discount totally the use of Marlon, etc. Today I might give it a chance as a good substitute for 'real' bronze.

The only thing sticking in my mind: what is the ability of a Marlon, etc. seacocks to structurally *withstand a - bolt of lightning* - exiting the boat through the plastic valve? ... OR if the plastic valve has a high dielectric (insulating) value, am I simply asking for a hole in the hull nearby the plastic valve? 
Being 'hit' several times I have some confidence that a bronze valve _should_ have 'no problem' with such a discharge.


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## RegisteredUser (Aug 16, 2010)

mitiempo said:


> And then along came Trudesign from New Zealand with a different approach that also meets ABYC standards. Their valves are better built than the Forespar ones are as well.
> 
> Marine | TRUDESIGN


My boat is getting all TruDesign below the waterline next week.


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## FreeAgent (Apr 19, 2017)

RichH said:


> *Marlon* and other 'plastic' seacock valves have vastly improved over the years. .............
> A few years ago I would discount totally the use of *Marlon*, etc.


There is a plastic called Marlon, but I presume you are referring to Marelon, the product Forespar uses in their sea cocks.



RichH said:


> The only thing sticking in my mind: what is the ability of a* Marlon*, etc. seacocks to structurally *withstand a - bolt of lightning* - exiting the boat through the plastic valve? ... OR if the plastic valve has a high dielectric (insulating) value, am I simply asking for a hole in the hull nearby the plastic valve?
> Being 'hit' several times I have some confidence that a bronze valve _should_ have 'no problem' with such a discharge.


It is hard to understand why lightening would preferentially ground through a plastic valve or thru-hull. By the way, it is OK to use a Marelon valve on a Bronze thru-hull and still have the thruhull bonded to the boats ground system. Don't know if that would help.

I know of one case where a boat mast was hit and it blew the plastic knotmeter thruhull right out of the boat. It was presumed that the transducer wiring that was near the mast allowed the flow of static to jump to the wire and find a path to the thru-hull. The boat was flooded and would have sunk, except it was a tri and floated on the outer hulls!

Lightening is hard to understand and hard to protect against. Owner of tri, after repairs, put one of those dissipators at top of mast. Does anyone use bronze thruhulls for instrument transducers these days?


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## Skipper Jer (Aug 26, 2008)

So I am getting the impression that boats equipped with Marlon, Marelon and other 'plastic' ABYC approved seacock valves and thru hulls are not an item to kill a deal over or would be a reason to deny insurance.


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## colemj (Jul 10, 2003)

RichH said:


> The only thing sticking in my mind: what is the ability of a Marlon, etc. seacocks to structurally *withstand a - bolt of lightning* - exiting the boat through the plastic valve? ... OR if the plastic valve has a high dielectric (insulating) value, am I simply asking for a hole in the hull nearby the plastic valve?
> Being 'hit' several times I have some confidence that a bronze valve _should_ have 'no problem' with such a discharge.


It is impossible to bond Marelon seacocks and thruhulls to anything that can conduct electricity, so there is no need to worry about this at all. To lightning, Marelon looks like any other part of the hull in an electrical sense. I suppose a bolt of lightning could by chance exit the boat next to a thruhull, but this wouldn't be any different outcome than if the thruhull was bronze.

Many depth sounders and speedos are Marelon or similar plastic, yet nobody worries much about lightning with them.

You should have much less confidence with bronze thruhulls in a lightning strike. Many, many reports of these being blown out or causing adjacent hull damage by lighting. Metal shafts, bearings, keels and struts have the same problem. I've never heard of a report of Marelon doing such.

Our boat is all Marelon (12 of them), we have taken a massive direct strike once, and three side swipes, with no damage to the thruhulls or adjacent laminate.

Mark


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## RichH (Jul 10, 2000)

Sorry to disagree, as I have personally witnessed a boat with plastic seacocks and no 'grounding'/bonding to the water surface, which took a lightning hit and which the surge exited _through the hull_ surface .... resulting about a million± 'teeny hull weepers' (sweat-like leaks) by which the hull was later condemned by the insurance carrier; hence, the concern. This is not based on anecdotal evidence but a probability of 'actual' based as a first person witness. I assume that lightning strikes can cause all sorts of hull-exit problems sometimes 'through' the FRG ... if one follows the former renown lightning 'guru' of FSU @ marinelightning.com. Bottom line is Ive had 3 major strikes over the years and not much damage to hull nor structure (a simple star burst exit through the side of an encapsulated keel) ... but twice had 'frozen'/damaged bronze seacocks (among 'other things') as a result of definite 'high amperage events'.


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## FreeAgent (Apr 19, 2017)

RichH said:


> Sorry to disagree, as I have personally witnessed a boat with plastic seacocks and no 'grounding'/bonding to the water surface, which took a lightning hit and which the surge exited _through the hull_ surface .... resulting about a million± 'teeny hull weepers' (sweat-like leaks) by which the hull was later condemned by the insurance carrier; hence, the concern.


So, there was no damage to the plastic thru hulls? Just the hull perforated because there was no other path to ground?

The case I saw first hand and described upthread, was probably similar. In that case, the tri probably did not have a path to ground through the hull. The weakest spot was probably the knotmeter thru-hull, so it blew out. However, now I think of it, I think the West system hull was also partly perforated.

Most of our keelboats with external lead keels have (or should have) all metal parts including bronze thru-hulls bonded together and grounded via keel bolts to the lead keel. Much less likely for thru-hulls to be affected, especially if they are not metal. For composite boats with encapsulated keels or no keel, like multihulls, a ground plate should probably be provided.


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## RegisteredUser (Aug 16, 2010)

I have looked around...

Do you guys have any links to good, solid, definitive info regarding lightning protection on sailboats?


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## FreeAgent (Apr 19, 2017)

RegisteredUser said:


> I have looked around...
> 
> Do you guys have any links to good, solid, definitive info regarding lightning protection on sailboats?


This article from Practical Sailor and the comments at the bottom may be of interest. Basically comes down to following ABYC recommendations and then hope for the best!

One more anecdote about how fickle lightening can be. At time we owned a Grampian 26. I somehow doubt it had any grounding or lightening proyection. It did have an external cast iron keel, but the mast was deck stepped. We were tied up alongside the wall at a marina. On shore, about 6 ft from us, there was an electrical pole that carried overhead wiring. The pole was wood and about 1/2 the height of our aluminum mast. We were out having dinner when a storm came through. When we got back, we saw that the wooden pole had been hit and split in two. No problem on our boat (which had plastic through hulls for instruments) Another Grampian moored near us had burn marks where forestay attached to stem. But no other problems.

On shore, engineers seem to know how to protect building and things like substations and chemical plants. But boats??? One paper suggests we protect boats in same way as buildings. This article talks mainly about power boats, but it sound as though bonding everything metal on deck, like pulpits and stanchions will provide some protection. Note: I only glossed over the article.


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## JimsCAL (May 23, 2007)

FreeAgent said:


> I know of one case where a boat mast was hit and it blew the plastic knotmeter thruhull right out of the boat. It was presumed that the transducer wiring that was near the mast allowed the flow of static to jump to the wire and find a path to the thru-hull. The boat was flooded and would have sunk, except it was a tri and floated on the outer hulls!


I am aware of a similar case. Many years ago, a young couple in our club had just bought their first boat, a Ranger 22, and had just brought it around to the club. They were at the dock sitting inside when the boat was hit by lightning. It also blew the transducer out and the boat began to take on water. Luckily they were able to stop the flow and avoid sinking. They named the boat "Zapped".


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## colemj (Jul 10, 2003)

RichH said:


> Sorry to disagree, as I have personally witnessed a boat with plastic seacocks and no 'grounding'/bonding to the water surface, which took a lightning hit and which the surge exited _through the hull_ surface .... resulting about a million± 'teeny hull weepers' (sweat-like leaks) by which the hull was later condemned by the insurance carrier; hence, the concern. This is not based on anecdotal evidence but a probability of 'actual' based as a first person witness. I assume that lightning strikes can cause all sorts of hull-exit problems sometimes 'through' the FRG ... if one follows the former renown lightning 'guru' of FSU @ marinelightning.com. Bottom line is Ive had 3 major strikes over the years and not much damage to hull nor structure (a simple star burst exit through the side of an encapsulated keel) ... but twice had 'frozen'/damaged bronze seacocks (among 'other things') as a result of definite 'high amperage events'.


I'm confused - you didn't even address thruhulls with regard to lightning in this post, and I don't see anything in the example that points to plastic thruhulls as being prone to lightning damage.

FWIW, I have seen the same as you describe on boats several times with bronze thruhulls. A quick walk through google will show you many more.

What you describe above is the lack of a lightning bond in the boat. This is completely independent of the type of thruhull used in the boat. Lightning bonding through bronze thruhulls is a gamble at best, and never a good idea. Bonding of bronze thruhulls is done for galvanic reasons, and they should be electrically separate from a lightning bond.

The safest combination for both lightning and corrosion is a robust lightning bond system and non-metal thruhulls. Any combination other than that increases the risk of damage from either.

Mark


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