Boat U.S. - March 2008 - (Page 41)

From the Files of DIY Boat Owner Magazine tioning system circulating water discharges and bilge pump outlets. Livewell drains present another situation on powerboats. Just power down in reverse or be out on rough water with a following sea and watch the livewells fill and possibly swamp a smaller boat. Install only approved composite fittings. A UL label on this Marelon ball valve assures quality. Thru-Hull Buyer Beware Many freshwater boats were equipped with all brass thru-hulls and seacocks and, in some cases, a bronze body but brass valve, sometimes with a pot metal (ferrous) handle, or brass or stainless-steel nut. There is no way of telling the difference visually between metal fittings of hardware quality and those acceptable for marine use. However, if it’s a stem-style valve, it’s likely brass; if it’s a brand-name seacock like Apollo, Groco, Perko or Wilcox, among others, sold in a marine store, it’s likely bronze. If you’re planning to use a boat so equipped in saltwater, you must replace all valves. Corrosion will inevitably cause them to fail. Be suspicious of low-priced seacocks when purchasing new ones. Look for an all-bronze body, non-corrosive handle and chromed-bronze ball. When in doubt, buy a recognized brand name. When purchasing composite “plastic” fittings look for the UL-1121 stamp of approval. An acceptable plastic reinforced nylon is Marelon, a fiberglass-reinforced nylon. The advantages of installing these composite fittings are obvious: corrosion resistance being the main one; no need for electrical bonding and they can be installed in metal hulls without needing to isolate. Important to note: Don’t connect together metal and plastic fittings. Their expansion coefficients are very close but a male metal fitting mated to a female plastic fitting could be a bad marriage. An example of this is coupling a bronze thru-hull with a Marelon valve. Never use ABS, PVC or polycarbonate thru-hulls or seacocks for marine applications. On all below-waterline hoses, providing the seacock’s hose barb is long enough, a double-clamped hose provides peace of mind. Screws should be opposed as shown. Note tags to identify usage and drain plugs for winterizing. These sample installations have the potential for a sinking should a clamp or hose fail unless equipped with seacocks: (left) Mid-size sailboat’s cockpit drain hoses lead to a fabricated manifold and to a single thru-hull, that when inspected, was installed just at the waterline when the boat is stationary. Once heeled, the thru-hull would surely be submerged. Red-White brand stem-style valve is likely hardware store quality brass (far left). Marine grade seacock is most likely bronze (at left). Gate valves (right) don’t belong on any boat. Most are made of metals that can’t stand the corrosive nature of the marine environment; they are slow to operate and you never know if they are open or closed. Their mechanisms are easily obstructed by marine growth, which results in incomplete closure. To Bond or Not Most experts don’t recommend the bonding of electrically isolated metal thruhulls and seacocks. The only exception is where fittings are below the normal bilge water level to protect against stray current corrosion. Of course, it’s not necessary to bond composite thru-hulls or seacocks. — By Jan Mundy Jan Mundy is the founder and editor of DIY. Each issue of DIY Boat Owner Magazine is filled with hands-on maintenance and repair features. To subscribe, see page 43 Bad: This thru-hull fitting (top left) connects to an in-line valve that connects to a threaded hose barb, then to a hose resulting in an inherently weak installation and one that doubtfully withstands the ABYC test that requires: “A seacock mounted so that the system will withstand a 500-pound static force (“lead weight”) applied for 30 seconds to the inboard end of its connecting fitting, at any point in its most vulnerable direction, without the system failing to perform as intended.” Best: Single-piece seacock assembly (left) mechanically fastened to the hull distributes torque loading and stress across the entire cast base. Note that clamp screws are in-line instead of opposed. BoatU.S. Magazine March 2008 41

Table of Contents Feed for the Digital Edition of Boat U.S. - March 2008

Boat U.S. - March 2008 Contents Behind the Buoy BoatU.S. Reports Member Forum Cap'n Drew Sailing the Sidewalk Aviators Ahoy Docking and Duffing Waterfront Living: Charleston Waterfront Marketplace Grady Right 2nd Time Around DIY: Keeping the Water Out Hot Tips Boat Smart Ask Chuck Foundation Findings Tangled Line At Your Service Good Foundations BoatU.S. Exchange Behind the Boat Where Our Flags Fly

Boat U.S. - March 2008

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