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  Topic Review (Newest First)
01-15-2014 01:00 PM
Re: Through-Hulls

For what it’s worth. I’m not really addressing this for just BubbleheadMD’s consideration, but for those boaters simply looking for some additional information.

I admire anyone who’s made circumnavigated, and twice is even more impressive. Bermuda is the farthest my wife and I have sailed. However, FWIW, his sailing skills and anecdotal evidence of no problems, no matter how extensive, really aren’t applicable here.

Regarding your statement about water absorption and desorption in Marelon , you are correct in part.

1. Dupont Zytel nylon 70G13L and Zytel nylon 8018 both absorbs and desorbs moisture at specific rates depending on the material composition, temperature, etc.

2. You use the term, “totally reversible”, in describing the absorption and desorption process, in theory you’re correct, from a practical perspective your boat’s Marelon fittings, in an Annapolis boatyard setting, will never, at the start of a new season, be anywhere near “full strength.” The “DRY AS MOLDED” (DAM) value, what you term “full strength,” is used by the ABYC, but it is a manufactured value, it doesn’t exist in nature. The DAM value is used in the molding process, some materials can be molded with a significant amount of moisture, other materials require almost no moisture. And in a marine environment, the only real useful value 100% relative humidity.

In an Annapolis boatyard, you’d be lucky to find a Marelon fitting at less than 65% relative humidity (RH). In fact, today (1/15/14) the humidity in Annapolis is 100% and the January average is around 65%. My guess is that your boat’s internal January average humidity will be closer to 75%. Also, remember the lowest humidity usually occurs on the coldest days and adsorption and desorption is slowest in cold weather and highest in warm weather. In fact, at below freezing temperatures, it almost stops.

Let’s see how your boat’s Marelon fittings will fare.

Zytel 70G13L (AKA Marelon) Flexural Modulus DAM = 700,000 psi.
50%RH = 400,000 psi
100%RH = 250,000 psi

Please note, the Dupont Zytel 8018 used in the 93 thru-hull fittings has a much lower DAM flexural modulus and tensile strength than the 70G material.

So at the start of the season you can expect to have a Flexural Modulus value of about +/- 350,000 psi. That’s a starting value of some 72% of the total loss potential. That’s a far from a “full strength” start for the season. And remember, high quality PVC can have a flexural modulus of around 350,000 to 400,000 psi and has very little impact from humidity, like 5% max vs. 60% for Marelon. I’ve worked with a plastic that has exceptional impact strength (about 10 times that of Marelon) that in a 28 day moisture test lost no more than 6% of its strength. And that loss occurred within the first 6 days of testing and there it stabilized.

There’s a lot more to be said, the effect of residual salt left in the nylon, the effect high levels of water in the nylon at freezing temperatures. I know of a ski rack manufacturer who learned the hard way about that problem.

If you or anyone else, for what ever reason, choose to replace the Marelon 93 flanged valves, you will have an over sized and odd sized hole that will need re-glassing and drilled before putting in a more standard thru-hull. The ID and OD of the Forespar 93 are totally non-standard.

When I refer to impact, I’m not talking about only internal impact, but also external impact. The longer a boat with Marelon thru-hull fittings (849 or 93) the greater the potential for impact related problems. External impact is probably more disastrous than an internal one.

Here’s a simple example, this happened to me in the Elizabeth River on the Chesapeake We sailed from Sandy Hook, NY to Norfolk, VA and about a ¼ mile shy of the Hospital Point anchorage (it was blowing about 10 kts and sunny) we were motoring at about 6 kts and hit a submerged something quite hard. When I dove on the hull I found a 4 ft long, ¼” deep gouge about 6 inches below the 2 galley thru-hulls. From the motion of the boat, the sound of the hit and the gouge I’d say the object was not small and had some heft to it. If those thru-hulls were Marelon and the object had hit 6” higher at least one, if not both, thru-hulls would have been destroyed. I know what the effect of such an impact would do to a Marelon fitting, especially at full saturation or 50% saturation for that matter. It wouldn’t matter if it were my boat, your boat or an experienced circumnavigator’s boat. In a flood, the stuff coming down the Chesapeake or the Hudson for that matter is a disaster waiting to happen.

I’ve taken apart both an older and current Forespar 93 seacock, and I can say that there was no handle redesign. There were several problems with the 93 that I’ve been aware of and they all dealt with the nylon threads that the SS handle lag (?) bolts screw into. The only changes I noticed were (a) the “ball section of the ball/attachment unit” has been improved and (b) they replaced the screw used to hold the handle to the ball unit. It’s now slightly smaller with a sheet metal type thread. A handle redesign is somewhat a stretch.

My biggest problem with Forespar is that this isn’t the first time they’ve had serious know problems with their products. The reason they built the 93 series was to try an solve 2 major problems with the 849. Yet, they never told the public about the problems on the 849 and continued to sell it as if it had no problems. In fact, even today, many marine “experts” still think the 849 unit is ABYC approved. They’ve never told anyone, recalled the products, or offered a fix.

There is a lot more on the Forespar topic than I’ve presented here. I hope to have a blog up and running in February discussing this and other marine issues. I’m trying to write an article or series of articles on this topic. Thru-hulls and seacocks are to me a most important boating topic.

I’d love to get comments or questions, preferably by private post.
01-09-2014 07:31 AM
Re: Through-Hulls


I've installed my Marelon components over a year ago, so too late for that.
I already have the DuPont tables for Zytel, so no need to send them.

For what it's worth, the water absorption that occurs, is not cumulative, and is totally reversible in less time that your average, winter haul-out. DuPont's table says 125 days, and the properties of Zytel return to normal. So, when you relaunch after the winter, you start off at full strength.

I did step up a size when I replaced my failed, bronze through-hull and ball valve. The old installation also incorporated a 90 degree elbow, which further impedes flow. The new installation is larger, and straight. My engine is getting plenty of water.

FWIW, I have a friend who has done two, complete, double-handed circumnavigations who uses Marelon seacocks for every hull penetration. He does agree with some of your concerns, but doesn't seem to feel that Marelon should be avoided "at all costs". He feels that for someone with my level of attention to maintenance, I am safe enough.

Between my installation, and the handle redesign, I am satisfied that my lone, Marelon fitting is safe enough until my next, major refit.
01-08-2014 11:42 PM
Re: Through-Hulls

Mitiempo - You're correct, what materials standards ABYC had (tensile strength and flexural modulus) have been removed. What's left for material standards is in UL 1121? And you're right the NZ company Trudesign makes a fairly standard designed nylon based ball valve and thru-hull. The material is about 30% glass filled low water absorption nylon. The ball valve design is far superior to the Forespar one as is the material. But unless TruDesign wants to go the Forespar route and create super thick thru-hulls, they're smaller sizes won't handle the hanging weight test.

I believe the new Forespar 93 was designed to try and accommodate a poorly chosen material.

Again. if you want a plastic ball valve or thru-hull
01-08-2014 06:09 PM
Re: Through-Hulls

Originally Posted by Watercolor View Post
BubbleheadMd –

Also, Gary states that, “Marelon is the only plastic that meets the rigorous ABYC standards.”

This is simply not true. There are at least 24 plus plastics that I know of that meet and exceed the ABYC standard.

As far as I know ABYC does not test materials - ie plastics - but finished products. If that is true ABYC would only test seacocks that were made of any particular material and presented to them for testing. I have only heard of one other seacock made of synthetic materials and they come from New Zealand if I recall. And even if the material was satisfactory that doesn't necessarily mean that the finished product is going to meet their standards. It is conceivable that a good material can be used to make an inferior product that doesn't measure up.

I work at a marine store that sells both bronze seacocks and through hulls - Groco mainly but other brands also - as well as the Forespar Marelon seacocks. I personally would not buy a Marelon through hull or seacock.
01-08-2014 05:29 PM
Re: Through-Hulls

BubbleheadMd –

I really appreciate your response, you’re absolutely correct in asking for verification re. what I’ve written on this thread. Just like you, this information challenged my assumptions of marine products and the ABYC. I’ll have more on the ABYC at a later time.

By the numbers.

1. Please hold off on the purchase of a Forespar seacock, I think I can show you enough evidence to convince you about Marelon and Dupont Zytel nylon strength loss and moisture absorption. However, if you’re purchasing a ¾” Forespar 93 flanged valve to service an existing function that requires a ¾” flow rate you will need to go up to the 1 1/4” size. The reason is that the 93 series thru-hulls are a really odd ball size, unique to the 93 only. The ½ and ¾” utilize the same thru-hull so the ¾” ID .62” is undersized. A normal thru-hull calls for an ID of around .70”. The Forespar 251 thru-hull ID for the 849 flanged seacock is .69”. You would have to go up to the 1 ¼” if the requirement called for a full .70” ID flow capacity.

This info can be found on pg. 41 of the Forespar catalog.

2. It would take several months to fully saturate the seacock. Additionally, the rate of saturation increases at a decreasing rate over time. So it might reach 80% saturation in 3 weeks and the last 20% might take 6 weeks. This is also info available from Dupont.

3. Regarding the carbon fiber issue. First, you really need to watch the video, at least the first 50 seconds. I just tried loading the video and for some strange reason it’s not available. Luckily, it is still on Youtube
or on Youtube Wes Gary why marelon?

If for some reason it’s taken off Youtube all I can do is quote the basics of what Wes Gary said.

Wes Gary comes on holding a Foresar 849 flanged valve and he says,

“HI, I’m Wes Gary, I’ve (done this, that etc,...........)
“I know polymer composites very well.
“I’m here to talk to you about Forespar’s plumbing fittings. I know that Marelon is not just a plastic, but an engineered carbon fiber and glass reinforced composite polymer ideally formulated for marine use?”

Forespar did, for a short time, make a limited batch of 93 series ball valves made from carbon fiber. But, according to Forespar they abandoned that project long ago. And as I can prove, Marelon is simply Dupont Zytel 70G13L 13% glass filled nylon.

Also, Gary states that, “Marelon is the only plastic that meets the rigorous ABYC standards.”

This is simply not true. There are at least 24 plus plastics that I know of that meet and exceed the ABYC standard.

It’s important to note that this is a closely scripted, paid, advertising video, not just an amateur video. Also, here is a Forespar document that shows several items under the heading “Carbon Reinforced.” Again this is all scripted to present an image of innovation and strength.

a. Note that the word FIBER is omitted.
b. I can say comfortably that NONE of the products presented in that picture are or ever were made of “carbon fiber” and that’s according to Forespar. I have the email to prove it.
c. Interestingly, the black products might have carbon in them, “CARBON BLACK” that is, to create the black/UV resistant color. But that carbon is not for strength, and may even decrease the material strength slightly.

I cannot sent the Carbon reinforced document via Sailnet, it's simply too big. If you want to send
me your email in a private message I'll be happy to send you all three documents I have for you.

4. On page 32 of the Forespar Catalog, you’ll see a table Forespar uses to suggest that Marelon is a close second to bronze. However, the tensile strength and flexural modulus values presented there are for Dupont’s Zytel 70G33l 33% glass filled nylon. How do I know? It’s the material we tried using for the original molding. Marelon is Dupont Zytel 70G13L 13% glass filled nylon (more on that later) and we wanted to use a stronger material. On pg 33 of the Forespar Catalog you'll see Forespar's values for the real Marelon. Compare the two sets of numbers. This was no mistake, it's been out there for years, and they've known about it.

I’m also including the Dupont table for all the 70 series Zytel products. You’ll see that both sets of Forespar’s values for Marelon co-inside with the Dupont numbers. There’s no need to test them, Dupont has already done that, and it’s their testing equipment and their product so they will always want the better values. Remember tensile strength and flexural modulus are the defined ABYC testing characteristics. You can do the exact loss percentages at saturation, my 60% was a rounded value. The actual values are: Tensile strength 57.1% loss and Flexural Modulus 64.3% loss at full saturation.

Again, I cannot sent the Dupont Zytel document via Sailnet, it's simply too big. If you want to send me your email in a private message I'll be happy to send you all three documents I have for you.

Additionally, I’m providing you with a document that Forespar provided UL when they were testing the 93. You will see the Dupont 70C13L very clearly referenced, along with the thru-hull fitting material 8018 WT listed. This is a new form of Marelon, that has less strength than the “original” Marelon listed in Forespar’s literature.

Again, I cannot sent the Forespar document via Sailnet, it's simply too big. If you want to send me your email in a private message I'll be happy to send you all three documents I have for you.

I hope this is of interest. If anyone want the unattachable files please send me a private email with your email address and I'll send the info out. I can assure you it is as I as I represented it.

Fair winds,

01-08-2014 04:35 PM
Re: Through-Hulls

Onr point to consider if thinking about Marelon. The Marelon seacocks require a larger hole for the same internal diameter and it would make going back to bronze later complicated at best.
01-08-2014 07:40 AM
Re: Through-Hulls

I can't play the video where I'm at, at the moment.

In your quote, you use the word "carbon fiber".
Nowhere, in their written documentation do I see the words carbon fiber.
Never, did I believe that Marelon incorporated carbon fiber.
My understanding, (in my own words) was that Marelon is a glass reinforced plastic, formulated for below waterline use.

There appears to be a conflict between what Forespar is publishing on their website, and what you're saying DuPont says about the tensile strength and flexural modulous, so I don't know the answer to the question.

Either you are incorrect about what you think Forespar is using for materials, or Forespar is publishing incorrect numbers.

Shifting away from the material properties for a moment, and looking at the design-
My recent investigations show that Forespar redesigned the handle around 2009 so that a handle failure does not result in blowing out O-rings or a leak that cannot be plugged with a wooden bung.

Also, since you claim that Marelon is nothing more than DuPont Zytel, and will lose 60% of its strength when saturated with water, I'm going to purchase a 3/4" Marelon through-hull and a matching, flanged seacock. I'm going to submerge them in seawater for two weeks.

I'll install them in a manner similar to Maine Sail's test, and put them on a trusted friend's load cell to see if the installation fails at 60% reduced strength.

BTW- Exactly how long do you think DuPont Zytel needs to be submerged in water, in order to become "saturated"?
01-07-2014 10:05 PM
Re: Through-Hulls

BubbleheadMd – Let’s not get into a mudslinging contest. It’s possible you’ve misread what I said. You did make the following statement, “Marelon through hulls and seacocks meet the ABYC standards.” The fact is that many knowledgeable boaters and boater professionals and experts have made the same statement. I would never accuse any of you of lying about that topic. If it was not for a molding project I was working on, I most likely, based on the information available, would have made the exact same statement as you did.

In fact, there was a substantial amount of money expended to find out that Marelon had some serious problems when it came to marine applications. We made the same assumptions based on the information available to us that you made. The molder, a wise old gentleman (a non-boater) said “it’s sometimes important to know the answers, before you ask the questions.” It’s the assumptions (the questions we don’t ask) we make that can kill us.

It’s those assumptions we make that give us a false sense of security that I believe give old Mr. Murphy a real leg up. And we all know that, on a boat, Mr. Murphy’s on steroids.

For example, the ABYC uses the term “standards” rather loosely. In their documentation they refer to their “standards” as merely “guides for design, construction, installation, and maintenance.” They aren’t the kind of standards that most people think of, like ASTM. In my discussions with ABYC they were clear to make that distinction.

So to anyone willing to give it a try, here are the two questions I asked in my previous post. I'd love to see you try and answer them correctly. These are not meant to be trick questions. I’m not doing this to make anyone look foolish. They do relate to the issue of assumptions we make.

After each question, I’ve provided a site that has “an answer.” The first relates to a Forespar formulated chart that compares Marelon to bronze, and a few other materials. The second relates to the question “What is Marelon?”

1. What is the tensile strength and flexural modulus of Forespar's Marelon?

2. Is the seacock that a Wes Gary is holding in the Forespar video made of an "engineered carbon fiber and glass reinforced composite polymer ideally formulated for marine use?
What Is Marelon


01-07-2014 02:41 PM
Re: Through-Hulls

Originally Posted by Minnewaska View Post
I'm not going to pretend this point is a scientific argument. However, I doubt the big production boat companies switched to Marelon because it was superior, rather because it was cheaper. Maybe I'm wrong.
Actually, builders use any given material for a host of reasons. Cost is one, so you're not wrong.
Thing is... it's not always simple. Example would be that the majority of boats sold in the last (pick a round #) 20 years are going into a less-knowledgeable "second home" market. Nothing wrong with that, but this translates into thousands of boats sitting in marinas 95% of their lives, permanently on shore power connections. By using the Marelon fittings, one source of trouble, loose electrons consuming thruhulls, is eliminated.

While our little YC moorage has pretty much state of the art power service, at regular expense, there are always complaints from other owners about their "Hot" marinas and all the problems with zincs going away quickly.

So, again, you are not wrong.... but there are more factors to consider.

And then, on the illogical side of marketing, owners of high end boat like Morris or Swan tend to want bronze everything and will pay more to get it.
Buyers at the low and middle end of the market are more concerned with amount of boat received on a $ per # basis.... and this concern goes up quickly at the low end of the production boat market.

FWIW, I have no "dog in this fight" having put all bronze thruhulls in our prior boat and then changed out the factory Forespar marelon fittings that were originally ball valves screwed onto threaded thruhulls and put back the newer Forespar one-piece seacocks from their "OEM line".

My solution works fine for me and since our moorage is electrically-well maintained, bronze would have been acceptable too.

01-07-2014 10:13 AM
Re: Through-Hulls


Do not accuse me of saying that your information was false or inaccurate. You cherry-picked a quote, and then accused me of calling you a liar.

I specifically stated that everything you posted was true and correct.

When I stated that Marelon was ABYC approved, I did cast my net a bit wide. I should have said "My Marelon" parts meet the ABYC installation standard. There is also wisdom in the post from the other forum that "UL approved parts do not necessarily make a UL approved installation".

I don't need to prove anything to you. Don't "challenge" me with information that is already published.

All that matters to me, is that my installation will withstand a 500 lb. hang test. It will not withstand a 500lb. "impact" or shock load, and I don't care. There is nothing, NOTHING stored anywhere near any of my through-hulls. Even if a battery were to break free in a knock-down, it physically would not fit anywhere near the nearest through-hull.

I respect Maine Sail and his level of caution is borne from a bad experience that never should have happened in the first place. Nevertheless, his tests are insightful and valuable. They are useful for making a risk vs. gain decision on through-hull installation.

I'm saying that for 99% of the recreational sailing or boating that people do, Marelon products, when properly installed, are acceptable.

It sounds to me, like ABYC needs to clean up their standards, and make them less ambiguous to prevent corporations from making public claims that their products meet industry standards. Allowing Forespar to claim that their fittings meet the ABYC materials standard, without rebuttal seriously dilutes ABYC's credibility in my eyes.

Why is this "standard" not a standard, as you say?
I'm reading the document now, and the word "standard" is used in nearly every paragraph. What are builders, and maintainers in the marine industry supposed to do? Follow the standard? Distrust the standard? Ignore the standard?

Oh wait- the final paragraph says:
The American Boat and Yacht Council standards are guides to achieving a specific level of design or performance...
So here's the bottom line:
You are here, spewing (true) numbers and factoids, in a histrionic manner, advocating expensive, International Space Station-level through-hull installations that many people will never need.

Using the "guides", I have achieved a specific level of design and performance that I find acceptable, for my level of risk.

I will totally agree with you one one thing though:
I'm looking at online ads right now. ALL of Forespar's Marelon products claim that they exceed UL and ABYC standards, and that they will never brittle with time, or temperature change.

Then, they acknowledge to Maine Sail that the smaller fittings do NOT meet ABYC H-27 500lb. static test, and their own documentation states that they do not meet the ABYC materials standard.

I am scratching my head as to why they have not had their a$$es sued off. Why is this allowed to continue?

My last question for you, and maybe Maine Sail:

Can either of you point me to a survey, news article or USCG report where a vessel was lost or nearly lost, due to the failure of a Marelon through-hull or seacock due to MATERIALS failure, not improper installation?

I don't care about broken handles. I want to see a report where the ball seal blew out, or the through-hull snapped off, or the valve body shattered.

These fittings have been in service long enough now, that if they were the death-traps you say they are, surely a vessel would have been lost by now.

EDIT: Ugh...apologies. You posted a link to the Catalina failure.
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