Seacocks - What Material ?

[cburger]

Originally Posted by colemj

Have you ever actually kicked and broken a marelon seacock, or do you just think it will break if you kicked it?

Mark

The point here is that Marlon will fail from impact before bronze and the chance that some heavy gear could shift and potentially snap it off causing a problem.

[micah719]

Bob is a resourceful and determined 30-year cruising veteran. If it doesn't break when he kicks it first time, he'll try again. On a serious note, I'll go with Bob on the bronze....and with the others on regular maintenance. Cburger's experience impresses me too, regardless of how cool his boat is.

[colemj]

Originally Posted by cburger

The point here is that Marlon will fail from impact before bronze and the chance that some heavy gear could shift and potentially snap it off causing a problem.

Again, is this just a feeling or do you have direct experience with it?

Marelon has a tensile strength of 27,000psi and a flex modulus of 1,300,000mPa.

Bronze has a tensile strength of 35,000psi and a flex modulus of 15,000,000mPa.

So while bronze is stronger than marelon, an elephant stomping on it will have a difficult time damaging it. It would take an engine in free fall for several meters to snap it off. In both cases, bronze is as likely to fail - particularly if it has any corrosion.

If one stuck to the argument that "it will fail before "X"...", then one would not choose bronze either.

I don't mean to just argue for the sake of it, but many people enter these discussions with opinions drawn from feelings and no evidence.

I would go with marelon, but definitely get the OEM 93-series products.

Mark

[Cheechako]

Although not a big proponant of Marelon, I can tell you that, breaking one off of the hull will not happen. In fact I spent hours removing one once (broken handle /shaft) trying to do just that. In the end I couldnt chisel it out piece by piece so had to wrap tape around a hack saw blade and remove it tiny piece by piece. I dont think you could break one on a cement floor with a sledge hammer. You might distort it though!

[HopCar]

Since I work in a marine store I hear about what works and doesn't work on boats. I've never heard of a Marelon seacock breaking off. The only issue with Marelon seacocks is exactly what Cheechako said. The shaft connecting the ball to the handle will break far easier than a bronze one. I've heard of several instances where this has happened. To prevent this you just have to exercise the seacock often enough that it doesn't stick. In a bronze ball valve seacock, you're much more likely to be able to break it free with out damage if it does stick. I keep an extension handle on my boat that I can add leverage to the seacock handle if I need to break it free.
Seacock Helper

[bobconnie]

Ive seen 5 yr old marelon so fragile from heat in the engine room they were installed in you Could break them with a small ball peen hammer !! I know I could have kicked it and done the same thing !! maybe on a Aluminum boat where they need to be used, ok but I don't own a aluminum boat so it is and will be Bronze for me !! just my 2 cents

[Fuss]

Originally Posted by bobconnie

Ive seen 5 yr old marelon so fragile from heat in the engine room they were installed in you Could break them with a small ball peen hammer !! I know I could have kicked it and done the same thing !! maybe on a Aluminum boat where they need to be used, ok but I don't own a aluminum boat so it is and will be Bronze for me !! just my 2 cents

Marelon does not deteriorate in sunlight, seewater or when exposed to engine room heat.
It does not do this in 1 year. It does not do this in 5 years.

The problem Marelon has is that it looks like normal plastic.
The problem bronze has that it comes in different qualities and looks a bit like brass.

I can assure you that a 5 year old marelon fitting, removed from a hot environment, exposed to seawater is not fragile and will not break with a small ball peen hammer.

I can assure you that a 5 year old plastic fitting, removed from a hot environment, exposed to seawater is very fragile and will shatter with a small ball peen hammer.

I have 8 year old marelon fittings. If I took one out , you could hit it as often as you like with a sledge hammer , you will deform it, but not break it.

[S/V Illusion]

Do any high end boat manufacturers use marelon valves?

[Sailorman375]

Problem with marelon is not the material, but the weakness of the stem and that fact they must be cycled often to avoid them seizing. Again, the stem is the weak link here. If you want the best go with either Sparton or Blakes. They have no equal, period.

[cburger]

Originally Posted by Sailorman375

Problem with marelon is not the material, but the weakness of the stem and that fact they must be cycled often to avoid them seizing. Again, the stem is the weak link here. If you want the best go with either Sparton or Blakes. They have no equal, period.

Absolutely correct

[cburger]

Originally Posted by colemj

Again, is this just a feeling or do you have direct experience with it?

Marelon has a tensile strength of 27,000psi and a flex modulus of 1,300,000mPa.

Bronze has a tensile strength of 35,000psi and a flex modulus of 15,000,000mPa.

So while bronze is stronger than marelon, an elephant stomping on it will have a difficult time damaging it. It would take an engine in free fall for several meters to snap it off. In both cases, bronze is as likely to fail - particularly if it has any corrosion.

If one stuck to the argument that "it will fail before "X"...", then one would not choose bronze either.

I don't mean to just argue for the sake of it, but many people enter these discussions with opinions drawn from feelings and no evidence.

I would go with marelon, but definitely get the OEM 93-series products.

Mark

I often make decisions based on instinct and gut feeling, not every decision in life requires a scientific study. On a shear load basis the plastic fantastic will fail way before a quality, flanged bronze properly installed seacock. "My instincts" tell me I could probably knock it off with one good wack with my 1lb hand sledge, way less than an engine falling from a couple of meters. As stated I have worked with both products.

[KatKokomo]

Thanks so much for your replies. It gives me a lot to think about.
I never used anything else below the water line but bronze.
A friend suggested using Marelon.
I am not sure what quality I will get here in Panama. I might have to order them from the states.

[JusDreaming]

Marlon for sure. We have been hit by lightning three times and no damage to thru hulls. Plastic vs lightning plastic wins

[micah719]

Does the marelon protrude outside the hull, meaning can it be damaged by de-fouling or something else hitting it a glancing blow?

Any chance it can be attacked by solvents, and how does it stand up to contact with fuels & oils?

What is the fatigue-resistance? What are the common failure modes for Marelon?

Sorry for the interrogation, just taking the opportunity to dig deeper.....here, this glaring desk lamp and cheap cigar smoke will add to the realism........

[Captain Bill]

Originally Posted by micah719

Does the marelon protrude outside the hull, meaning can it be damaged by de-fouling or something else hitting it a glancing blow?

Any chance it can be attacked by solvents, and how does it stand up to contact with fuels & oils?

What is the fatigue-resistance? What are the common failure modes for Marelon?

Sorry for the interrogation, just taking the opportunity to dig deeper.....here, this glaring desk lamp and cheap cigar smoke will add to the realism........

I can answer the first two. Yes the Marelon does prtrude outside of the hull, but they are available as either mushroom type fittings or countersunk flush fittings if you are extremely paranoid about mechanical damage.

I have inadvertantly exposed a couple of my Marelon seacocks to engine oil, diesel, antifreeze, and 90 weight gear lube with no apparent ill effects. Yes I'm sloppy but I do clean up after myself. They are also covered with hard bottom paint on the outside with no apparent effects from the solvents in the bottom paint. I also have Marelon raw water strainers on all of my intakes.

All of my Marelon fittings are now over 10 years old and I cannot see any deterioration in any of them and I've never had one stick.

I suggest you contact Forespar to see if you can get an answer to the third and fourth questions.