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Seacocks


pks1702

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Interesting piece from YBW site

A leading marine surveyor is warning yachtsmen that their boats could be in danger of sinking because thousands of seacocks and through-hull fittings are made from brass rather than bronze.

Paul Stevens, 58, a founding member of British Marine Surveyors Europe, is ‘incredulous' that some boatbuilders are fitting out yachts with brass ball valve-type seacocks which are designed for fresh water plumbing and piping systems.

In salt water, brass is prone to a form of corrosion called dezincification, which makes them brittle and subject to failure.

Mr Stevens has examined yachts where cheaper brass seacocks have corroded so badly that they snapped off in his hands on inspection.

‘It used to be the case that boatbuilders only ever fitted bronze seacocks which are virtually fail safe,' he said.

But bronze and DZR brass - which is resistant to corrosion - is four times the price of ordinary brass.

Ordinary brass will probably last five years, Mr Stevens admits, but if you introduce other factors, like electrical current leakage and associated electrolytic action (especially with marina shorepower), the rate of dezincification of brass fittings will be rapidly accelerated.

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Recently a boat sank in Portsmouth the owners comment:

The marine surveyor has investigated the boat and informed me that the cause was electrolysis of the macerator seacock. When the boat was lifted the skin fitting for this was completely absent! The seacock was forced into the boat leaving a sizable hole which caused the boat to take on water very quickly.

Where am I with the claim status? Paper-work submitted but no idea yet on repair costs, except far too big for me to cover out of our savings if the insurers won't pay. The insurer needs the repair estimate before they will tell me anything.

The work to produce an estimate continues, the parts required list is apparently very long and a quick estimate for repairing just the engines is around £12k + VAT assuming that various parts need to be replaced. The first aid work has prevented the engines from seizing-up.

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And a near miss

Dear reader, this thread involves a huge amount of maximum stupidity, and I'm lucky not to have lost my ship or any lives.

As regulars on this forum know, I re-engined my boat this winter with a new Beta 25, doing pretty much all the installation work myself, the engineer then checked everything before running up the engine and signing off the warranty. I then connected the seacock and hull-anode bonding wire to the engine block.

Two weeks later, returning from the first weekend cruise of the season, I found I had a dead engine starting-battery (although the day was saved by jump-starting from the domestic bank). As the battery was five years old, I reckoned it was finished and bought a new one at vast expense.

Last weekend, at anchor in Poole, we were about to go to bed when I chanced to check the engine battery voltage and found it dead! As we were on a bit of a lee-shore, I jump-started the engine and moved for peace of mind to an empty mooring-buoy for the night.

On returning to the Solent, we decided to spend the night in Lymington rather than head home to the Hamble, and the following day I had a local electrician on board to check what was going on. What in fact was going on was that I'd secured the seacock bonding wire to the starter-motor positive!! The meter was reading 16amps to the bonding circuit whenever the engine battery was on, whether we were running the engine or not. Bloody idiot! Complete bloody fool! Bloody hell!

We immediately shifted ourselves to the harbour wall, where at LW neaps we touched but ony half dried-out and at 1.00am I was in the water in a drysuit inspecting the damage (and avoiding floaters). We spent the rest of the night on alternate seacock-watches before a 6.30am call to the engineer I'd contacted the evening before who rocked up promptly and ordered all parts before the delivery truck left Aquafax at 8.00am. He also got the Yacht Haven to agree to an emergency lift-out first thing.

The damage:

* New 3/4" engine intake seacock - lost entire outer flange, half of threaded area and only held on by the brand new Sikaflex under the internal flange! (full replacement)

* Old 3/4" galley-sink outlet seacock - badly corroded and weeping (full replacement).

* Old 1/2" raw-water intake (to galley) - broke off in my hand (full replacement).

* Both old Blakes heads seacocks - outer flanges and bolts badly corroded (only replaced these parts)

* New MG Duff large hull anode - lost 1/4" all round (but still plenty left).

* New Featherstream prop anode - lost 1/8" all round (still plenty left for the season).

The only two seacocks that didn't seem effected were the heads sink outlet which is on the waterline (it was cleaner than before but hadn't lost any structural material), and the cockpit drain seacock, which isn't bonded at all (this might be to do with the fact that it also contains the heat-exchanger for the fridge?).

We worked non-stop during the day removing and replacing all damaged seacocks etc and fitting new, before being lifted-in last thing before the crew left for the long weekend.

Of everying stupid thing I've ever done, this - but for the grace of the ineffable - was the most cretinous. At best I'd have sunk my boat on her mooring. At worst I'd have put the lives of my crew and others at risk.

I take full responsibility for my idiocy.

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  • 3 weeks later...

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