Thru Hull Questions

[Larry B]

Be vary of marelon as it doesn't take much to break it.

According to this chart it looks pretty strong to me? How do you mean that it will break easy???

http://www.forespar.com/resources2/pdf/ ... PopRed.pdf

[TW28RJ]

Long chain polymers like polyproplyne break down over time and become fragil. It has to do with the complexity of the molecule, your not going to read on the marelon website. Sort chain poylmers like polyethylene are less likely to break down.. is marelon a long or a short chain polymer?

I personly wouldn't use marelon, and i wouldn't use stainless steel. Plastics expand and contract significantly more than metals which is somthing else to think about. If you want to learn more about stainless steel do a search on it's compatibility with chlorides..

[TomW]

Marelon is a proprietary blend of polymers that is the only one that meets AYBC standards for through hull standards. It has been around for arround 20 years and never been the source of a known failure. Here is Jacques feeling on Marelon:

I would go one step further and say that Marelon is superior to bronze.

He responded to someone saying Marelon was equal to bronze.

As far as Stainless Steel if you use 316 there will not be a problem as long as there is a current flowing past it, it is the lesser Stainlesses that causes problems. Saying that I would prefer bronze over SS in my below waterline fittings.

The other thing that causes problems is when different metals are used beneath the water line and there is an electic current in the water as sometimes happens at a marina. If you use different metals you need to run a grounding system to each fitting. This is simply a 16GA wire from fitting to fitting then to a grounding plate so that all fittings have the same grounding potential. Easieast way not to have to do this is stay with one material, all bronze or SS. Marelon of course doesn't have an electrical potential and can be used with either.

TW do what you want but having done my homework the above is what I have found out.

Now let's get this back to the dead horse category!!!!

[ks8]

Will there be electrolysis issues with any metal through hul and a graphite or CF bottom on the hull?

[TomW]

Think about a minute it KS, both are encapsulated in epoxy. They would need that stray electrical current, like might occur at a marina, even if they had a scratch in them to set up a current flow. If you sand the epoxy/graphite coating then you are expoxing the graphite but unless you have that electrical current it can't affect the fittings.

[majorgator]

I've pretty well determined that if you post an opinion (or known fact) on this forum, there will be at least 1 person that disputes it with their reasoning. When you get 5 or 6 or 7 people who who dispute it, then its worth listening to. Let's all remember that we're building BOATS, not nuclear power facilities. We're installing parts and pieces on a vessel that will be exposed to some of nature's most harsh environmental conditions; an environment which no one understands completely. "So I put a piece of metal on my boat and it corroded"..."The plastic fittings I put on got too much sun damage and eventually cracked" Yeah, duh! Point out any one production or custom boat that's more than 10 or 15 years old that has been used in saltwater, and if its all original (ie. nothing repaired or replaced), then I'll shutup.

One last plug for SST fittings below the waterline:
In the water/wastewater treatment facilities I build, we have 2 standards for metals that will be in submersion: aluminum and SST. You think that saltwater is bad, take a look at some of the fluids that come through these facilities. We build and design systems that forcefully incorporates excessive amounts of chlorine (gas and liquid), lime, carbon, ammonia, fluoride, sulfuric acid, and many other chemicals that you don't even want to look at without protective safety gear. Of course, different metals have their correct applications, and we avoid using them in a quick-sure-fail environment. The desalinization equipment we install is primarily constructed of SST. That is equipment that processes saltwater...and the components are in constant submersion. Other than the appearance, we don't find too many differences in 304 vs. 316. In general, we use SST for the fabrication of a variety of submersed applications, such as pipe fittings, brackets, trays, bolts, etc. Since much of our work is rehab and additions, we often remove old SST components so the system can be up-sized, and almost without fail, those pieces are in excellent shape.

We don't use SST fittings when installing chlorinators. For this, its almost always SCH80 PVC or bronze. The purpose of a chlorinator is force extremely high concentrations of chlorine into the system, often times 25% to 50% by volume. No matter what type of material you use for this application, the components are subject to frequent maintenance and replacement.

Saltwater is less than 2% chlorides. Chlorides have been identified to be corrosive to SST at water temps higher than 50C, or about 120F. Still, the exposure needs to be continuous and it takes a long time to matter. Since the water I fish in only ever gets to the mid 80's (in the heart of scallop season), I won't be too concerned. SST thru-hulls for me!

Hopefully, this is my last post on this thread

Seth

[cape man]

Seth,

LOVE IT!!! Well said!

[tech_support]

I know a 40' sportfish that sank at the dock because of a stray current in the bilge causing the rapid corrosion of a bronze through hull. They got to it before it got past engine room bulk head, but it could have been a total loss.

I have never installed or owned a boat (production or self made) where I used a sea cock on a drain. Most of us strive to make our boats much better than production boat, but at some point you use your experience (and other's if your is lacking) to make a decision.

Marleon fittings would be my preferred choice on almost any fitting for these boat, I know its not going to react with anything. But its not always the most economical or easy thing to find in the size or part shape you need.

[TomW]

Seth that's great!!

Now Shine will you kill this dead horse!!

[PJPiercey]

It's always the same cast of characters that can't stand to see a differing opinion on a thread after their own opinion. They feel they MUST have the last word. Don't waste your time. In "Profile" there's a tool called "Friends and Foes". Mark these characters as "Foes" and their posts will be invisible.