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Old 29-07-2014, 11:35   #16
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Re: Marelon Thru Hull Fittings

^^ Another thing I did not consider, since I keep the boat in the water in the winter, is the time a boat in on the hard.

My cat does have some above water line discharges (bilge, chain locker, sinks, propane well, tank vents), but like most cats, they are NOT exposed to the sun; they are located either on the underside of the bridge deck or between the hulls. None where the sun hits, so I didn't think about that. It is probably not an issue for the OP, not on any of the old boats I've owned, but it certainly would be for monohulls.
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Old 29-07-2014, 14:30   #17
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Re: Marelon Thru Hull Fittings

While we're on the subject of thru-hull materials, why do many European boat builders use brass thru-hulls? They call it marine grade brass (CuZn36) but as best I can tell, it has more than 30% zinc in it. Is there something special about this brass that you can use it in salt water with out the zinc coming out?

All of the American made thru-hulls, that I know of, only have about 5% zinc in them.
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Old 29-07-2014, 15:17   #18
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Re: Marelon Thru Hull Fittings

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Originally Posted by HopCar View Post
While we're on the subject of thru-hull materials, why do many European boat builders use brass thru-hulls? They call it marine grade brass (CuZn36) but as best I can tell, it has more than 30% zinc in it. Is there something special about this brass that you can use it in salt water with out the zinc coming out?

All of the American made thru-hulls, that I know of, only have about 5% zinc in them.
I have been working through exactly the same issue as the fittings on the boat are BSP (British Standard Pipe) mostly Parallel female and taper male.

Currently most everyone in Europe has shifted from Bronze to what is called DZR, from Wikipedia:

Dezincification resistant brass (DZR), also known as Brass C352,[1] is an alloy used to make pipe fittings for use with potable water. Plumbing fittings that are resistant to dezincification are appropriately marked, with the letters "CR" (Corrosion Resistant) or DZR (dezincification resistant) in the UK, and the letters "DR" (dezincification resistant) in Australia.

In fact, even Blake seacocks (the old tapered seacocks which have to be greased every season or two are now made of DZR.

As best I can tell, the performance is similar to Bronze.

The following is a really useful link:
Brass and Bronze
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Old 29-07-2014, 21:19   #19
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Re: Marelon Thru Hull Fittings

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Originally Posted by HopCar View Post
While we're on the subject of thru-hull materials, why do many European boat builders use brass thru-hulls? They call it marine grade brass (CuZn36) but as best I can tell, it has more than 30% zinc in it. Is there something special about this brass that you can use it in salt water with out the zinc coming out?

All of the American made thru-hulls, that I know of, only have about 5% zinc in them.
It has to do with EU requirements. In the new directives boat manufacturers have to use fittings that will last for at least five years. The high zinc junk isn't as good, but since the better bronze is much more expensive and it isn't needed to meet certification requirements for a builder there is no downside. For the end user however it is a problem.
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Old 29-07-2014, 22:24   #20
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Re: Marelon Thru Hull Fittings

The EU trend towards "five year" seacocks is likely to spread world wide (if it hasn't already) - although I imagine Spartan in Maine will be a hold-out.

Even if your name brand bronze seacock is actually made in the US or EU (and is it still?), how do you know where the bronze came from?

This is one of the reasons I switched 10 years ago to the Forespar OEM 93 Marelon seacocks.
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Old 29-07-2014, 23:09   #21
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Re: Marelon Thru Hull Fittings

I just installed Trudesign composite thru-hulls and ball valves. After looking at bronze and Marelon I decided the Trudesign would eliminate any concern about electrolysis and avoid the seizing issues of Marelon.
They have an IMCI certification, for whatever that means, and appear to be well made and very smooth in operation. I'll let you know in 20 years or so if they are any good.

One word of caution though: they come in both BSP and NPS so don't mix them up and be sure your supplier doesn't either. I bought thru-hulls and valves in NPS but when I went back to get the appropriate tailpieces they only had BSP in stock.

Having the thru-hulls epoxied into the hull gives me piece of mind.
When I bought the boat the surveyor condemned the bronze ones and 2 of the valves, so I've had that at the back of my mind ever since. Of course after cutting them out they looked as solid as new, but they weren't very hard to break loose.
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Old 29-07-2014, 23:14   #22
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Re: Marelon Thru Hull Fittings

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The EU trend towards "five year" seacocks is likely to spread world wide (if it hasn't already) - although I imagine Spartan in Maine will be a hold-out.

Even if your name brand bronze seacock is actually made in the US or EU (and is it still?), how do you know where the bronze came from?

This is one of the reasons I switched 10 years ago to the Forespar OEM 93 Marelon seacocks.
You ask the manufacturer for the certifications for the parts. Most reputable manufacturers can supply them, as they are required for inspected vessels.
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Old 08-08-2014, 16:09   #23
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Re: Marelon Thru Hull Fittings

I have put Forespar Marelon thru-hulls in hundreds of boats over 20 years, without any problems, would never go back to bronze and the required bonding.
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Old 11-08-2014, 12:55   #24
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Re: Marelon Thru Hull Fittings

I have all Spartan bronze seacocks and they are taken apart and greased every two years. They have been trouble free for 30 years and they spend 8 months a year in saltwater.
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Old 19-08-2014, 08:43   #25
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Re: Marelon Thru Hull Fittings

A shameless plug for HopCar's firm. Excellent service, good pricing on large Groco thru hull, valve combo. I couldn't beat his pricing let alone his delivery
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Old 19-08-2014, 08:57   #26
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Re: Marelon Thru Hull Fittings

Thanks Chris!
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Old 21-08-2014, 16:18   #27
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Re: Marelon Thru Hull Fittings

I have never seen a Marelon fail. But they have one big disadvantage in my opinion. I like to fair in a thru hull. You can't do that with these. Also, there is the possibility it will shear off if it hits a rock or something.

I would not use one below the waterline.
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Old 21-08-2014, 16:36   #28
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Re: Marelon Thru Hull Fittings

If your Marelon through hull hits a rock then that can only mean one thing - your keel has just fallen off. If that is the case then a damaged through hull might just be the least of your worries.
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Old 21-08-2014, 17:09   #29
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Re: Marelon Thru Hull Fittings

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Originally Posted by Night_Sailor View Post
I have never seen a Marelon fail. But they have one big disadvantage in my opinion. I like to fair in a thru hull. You can't do that with these. Also, there is the possibility it will shear off if it hits a rock or something.

I would not use one below the waterline.
When you say "fair in" are you talking inside the hull or outside? Hit a rock??? The material has the tensile strength of steel almost and there is not enough showing on the external hull for a rock to grab onto in the lottery chance it was hit by one. They also make them in a flush mount version if you don't want any lip showing. As a manufacturer I have used them for 30 years on hundreds of boats without a failure. Saves weight, no corrosion, no bonding. Would never go back to bronze.
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Old 21-08-2014, 17:28   #30
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Re: Marelon Thru Hull Fittings

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If your Marelon through hull hits a rock then that can only mean one thing - your keel has just fallen off. If that is the case then a damaged through hull might just be the least of your worries.
That is assuming you are in a monohull. These are common in multihulls for the weight savings. In any case, how do you fair one in?
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