Take off the top coat at inside hull at the mounting area. Drill the hole for the seacock through the hull by cup drill between 53 to 55mm diam. Place a lot of Sikaflex or similar putty under the flange of the seacock and by finger to the drilled area of the hull, push the seacock to its place so that you can see putty coming out everywhere around the flange. Look that the seacock is directed to the direction of the hose. Laminate some layers of GRP (glass reinforced resin) over the flange and the hull around it. Let all dry one day, go next day outside the hull and cut rest of the seacock coming out (same time body and piston).
When you are cutting. The handle of the seacock ought to be down and at locked position (green color up at the lever). We prefer this GRP lamination method without metal used and the Shakewell valve become part of the hull.
Install by 3 bolts: This is possible, but difficult to find bolts with conical heads to be flush with the boat bottom. (Bolts from outside in to the boat.)
Take off the top coat inside, drill the 53 mm diam. hole, putty like above explained, put seacock through the hole, drill 3 holes of 8mm through the flange and hull, make place for the conical heads of the bolts outside hull. Now take out the seacock from the hull, put lots of putty, put seacock at the hole, press a bit and put GRP laminate on flange. Next day cut flush.
Please, take off the inner layer of the laminate of the hull by a cup drill which has diameter 90 to 100mm ( so that the flange can go more down in to the Divinycel ). Drill by 53/55mm cup drill at center on this distance material and through the hull out. Scrape material out at the Divinycel to have seacock coming out at other side of the hull. Put Sikaflex on distance material a lot, press the seacock in and laminate on the flange. Make the same like at ordinary GRP hull informed above.
Next day cut smooth the outcoming part flush with the boat bottom.
Look our drawings on this page to make more clear how to do it.
use three 8mm bolts or screws.
To metal hulls: you need to weld an extra ring inside the hull about thickness of 10mm to give more needed thickness under the flange of the seacock.
Drill by the cup drill a 50mm hole at the hull for the seacock. Before welding the ring make three holes through it ( look drawing ) with 8mm threads. Through these holes mark at the flange of the seacock the drilling points, to have in proportion to the holes at the threaded ring. The threaded bolts have length not to touch the hull. Put the seacock with the ring at the 50mm hole of the hull. weld to fix the metal ring to the hull a bit. Take off the seacock and weld properly, screw the seacock and make flush with the boat bottom, use stainless bolts and some putty to make it water tight.
When you like to make service for the moving parts of the seacock you can do it afloat yourself easily. You need to have one Shakewell Blind Cup or complete Piston Device (complete valve mechanism) on board at a known place to find when needed. If you change the Piston Device: do it rapidly –take off the old one and put the new in. You could get that time one liter of water in, not more. Next time, when your yacht is on dry land you cut it flush with the boat bottom. If the piston comes a bit out, it makes very little drag compared to the hole of an ordinary ball valve.