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Friday, January 30, 2009

Cockpit Drain Thru-Hulls and Seacocks

Got the thru-hulls and seacocks for the cockpit drains this week. Per a previous post, we have decided to use Marelon fittings instead of bronze. Advantages of Marelon (a composite material) are: 1-does not corrode, 2-lighter than bronze, 3-cheaper than bronze. Yet they are UL approved and meet or exceed ABYC and ISO specifications for underwater thru-hulls and valves. These particular fittings, made by Forespar, are not the "off-the-shelf" fittings you find in the West Marine catalogs. These are the OEM-only "93" series. To see the difference the equivalent "off-the-shelf" Marelon fitting is to the very right in the picture, with the 93 series valves to the left. It is important to note that these are not "ball valves threaded onto thru-hulls", which is a big no-no on a boat, especially under the waterline. These are true seacocks with a flanged base requiring a backing plate. Some other differences to note:
  • these are "two piece" units: the thru-hull and the valve housing. The hose barb is part of the valve housing, not a threaded on "tail piece" like some other valves.
  • The thru-hull uses a straight buttress style thread, which is stronger than typical a pipe thread.
  • Units are a bit more compact than standard seacocks.
  • Other than regular opening/closing of the valve, they require little maintenance
And I love this feature...
All MARELON® integrated valves have a removable plug in the handle (white cap with loop). This plug is made to fit into the external thru-hull (non-screened style only). In an emergency, this plug can be placed in the thru-hull (water pressure will keep it in) and the valve disassembled while the boat is in the water. Someone must get wet, but the boat does not need to be hauled for valve repairs. By tying a lanyard to the cap, you need only get wet once.
This depends on how warm the water is of course (or if you got your drysuit with you). For more info see Forespar's website.
From Building A Westsail 42: Thru-hull Installations
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