Marelon Plastic Seacocks

KompetentKrew

KompetentKrew

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Hello again,

I have a seacock which is stuck in the open position and which therefore, presumably, needs replacing.

The surveyor marked this as a defect during the purchase process and said in this report:

the Surveyor said:
If fittings or seacocks are changed advice to use plastic ones. There is a type that is flush to the hull when closed.
Click to expand...

Does anyone recognise what he means by "a type that is flush to the hull when closed"?

Is this a specific brand of seacock, or can anyone identify the model?

Is the surveyor right to say this is the best kind?

Also, if anyone knows the cheapest place in Gosport to lift a 40' boat, that would be much appreciated, too.

I do appreciate all the replies to my recent threads, and I'm sorry for not contributing much myself - I am very busy at the moment, but do plan to follow up with all of them just as soon as I have the chance.
 
He means to say that the skin fitting instead of being domed is countersunk and hence sits flush with the hull.

Like this: https://aquafax.co.uk/product/3-80171-forespar-csunk-seacock-straight-12bsp

Best all depends on what you want, its definetely the most expensive type.

Flush vs domed all depends on how you use the boat, a flush seacock is best because there is less drag, however most boats sail happily with normal domed ones. A flush one requires a bit more time and finesse to fit correctly, but in terms of seaworthiness there is zero difference between them.

Regarding materials, the forespar plastic seacocks are very good with the advantage of not corroding, they're also very expensive. Brass is also absolutely fine as long as its 'DZR' brass, its what the vast majority of boats have.
 
Ceirwan said:
He means to say that the skin fitting instead of being domed is countersunk and hence sits flush with the hull.

Like this: https://aquafax.co.uk/product/3-80171-forespar-csunk-seacock-straight-12bsp

Best all depends on what you want, its definetely the most expensive type.

Flush vs domed all depends on how you use the boat, a flush seacock is best because there is less drag, however most boats sail happily with normal domed ones. A flush one requires a bit more time and finesse to fit correctly, but in terms of seaworthiness there is zero difference between them.

Regarding materials, the forespar plastic seacocks are very good with the advantage of not corroding, they're also very expensive. Brass is also absolutely fine as long as its 'DZR' brass, its what the vast majority of boats have.
Click to expand...

I am slowly replacing my metal skin fittings and seacocks with Marelon ones. As Vyv says they are a bit larger in diameter but they are a single unit of skin fitting and seacock so not as tall or 'fragile'. As to 'very expensive', that's rubbish when you look at the cost of a DZR skin fitting and seacock which the Marelon or Trudesign ones are in one.

As an aside, I had one Marelon seacock fail on me at the handle. Due to the design I was able to replace the seacock portion in the water with absolutely no water ingress in about 5 mins. I would not want to do that with a DZR set up.

I would not look at a metal seacock again.
 
Some of the plastic efforts are said to be quite good, others prone to failure, so not for me. Problem is I can't remember which is which

With ravishing new ideas you often don't find the drawbacks till a few years down the line. I would stick to Blakes; as they used to say in the computer industry:

"Nobody ever got sacked for buying IBM"
 
Ceirwan said:
He means to say that the skin fitting instead of being domed is countersunk and hence sits flush with the hull.

Like this: https://aquafax.co.uk/product/3-80171-forespar-csunk-seacock-straight-12bsp
Click to expand...
Many thanks.

I can't see myself taking the time out to do the countersinking right now, so I guess it'll be one of the mushroom head ones from the same supplier: https://aquafax.co.uk/catalogue/15942-sea-cocks

Ceirwan said:
Best all depends on what you want, its definetely the most expensive type.
Click to expand...
Surely "best" is the one with the lowest chance of failure or future corrosion?

I'm quite happy for seacocks to have free reign with my wallet.

Ceirwan said:
Regarding materials, the forespar plastic seacocks are very good with the advantage of not corroding, they're also very expensive. Brass is also absolutely fine as long as its 'DZR' brass, its what the vast majority of boats have.
Click to expand...
I think I'd decided long ago, from many previous threads here, that marelon is the way to go. I think the PO questioned this on the day of the survey, and the surveyor confirmed it's his preference.
 
I was on a visitor pontoon and a guy with a boat in front was pretty distressed as he said he had bumped the pontoon and sheered off a plastic through hull fitting. It was above the waterline so was probably a bilge pump outlet or similar but it did make me think about through hull fittings in "plastic".
 
C08 said:
I was on a visitor pontoon and a guy with a boat in front was pretty distressed as he said he had bumped the pontoon and sheered off a plastic through hull fitting. It was above the waterline so was probably a bilge pump outlet or similar but it did make me think about through hull fittings in "plastic".
Click to expand...
I suppose the countersunk ones would be less prone to this.

Does make for some scary thinking, though.
 
Can I ask a general seacock question?

My toilet seacocks are Blakes so I can service them every year and see for myself the internal condition. But my other seacocks are sealed ball valves - how do I know when to change them? Should it be every X years, or if they start getting difficult to turn, or if they start weeping or etc etc..?

How do other people decide when to change them? Thanks.
 
C08 said:
I was on a visitor pontoon and a guy with a boat in front was pretty distressed as he said he had bumped the pontoon and sheered off a plastic through hull fitting. It was above the waterline so was probably a bilge pump outlet or similar but it did make me think about through hull fittings in "plastic".
Click to expand...

If it didn't have a backing pad behind it the hull would flex enough to break it on the flange area.
 
Jonny A said:
Can I ask a general seacock question?

My toilet seacocks are Blakes so I can service them every year and see for myself the internal condition. But my other seacocks are sealed ball valves - how do I know when to change them? Should it be every X years, or if they start getting difficult to turn, or if they start weeping or etc etc..?

How do other people decide when to change them? Thanks.
Click to expand...

It's worth checking that they do what you think they are doing. One problem is that the stem fails but the handle turns as normal. You think you are operating it but you are not, as the ball remains where it is. So long as they function as intended keep using them.
 
LeeSan do a Trudesign kit, which includes skin fitting, seacock and tail, for various sizes at a price about the same as DZR.
Their website has all the spec sheets with dimensions if you are concerned about the size.

I have just changed mine and am very pleased with LeeSan and the fittings. A much better option than most modern metal ones in my opinion. Apparently even Blake’s seacocks are made with DZR have a limited life.
 
If the surveyor said "plastic" I hope he was talking about above water! Truedesign and Marelon are, I believe, the only non metal ones approved for use below water by the likes of Lloyds and ABYC. There are many plastic skin fittings available that are only suitable for use above water. I don't think either of those have flush fitting variants but happy to be proved wrong. Truedesign and Marelon are both composite materials and would never be described as plastic
 
ctva said:
As to 'very expensive', that's rubbish when you look at the cost of a DZR skin fitting and seacock which the Marelon or Trudesign ones are in one.
Click to expand...

The 1" Marelon through hull & valve is £77.64 RRP + VAT. So just over £93.

DZR 1" Through hull fitting from Marine Store £18.77
DZR 1" Ball valve fitting from Marine Store £22.06.
DZR 1" Male hose connection (for 25mm hose, same as the Marelon) from Marine Store £7.89.

So £47 vs 93.
Or twice the price.
 
Ceirwan said:
The 1" Marelon through hull & valve is £77.64 RRP + VAT. So just over £93.

DZR 1" Through hull fitting from Marine Store £18.77
DZR 1" Ball valve fitting from Marine Store £22.06.
DZR 1" Male hose connection (for 25mm hose, same as the Marelon) from Marine Store £7.89.

So £47 vs 93.
Or twice the price.
Click to expand...
Ok, but not “very expensive” and four joints as opposed to two and multiple time the life span of dzr and no electrolysis and far better mechanically. Considering the importance of below water skin fittings and the cost of the boat, it’s a no brainer. At least to my simple brain anyway.
 
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