The installation looks great Lngmar. Can you further explain the install? Is that a backing plate covered in sits at the base?
My installation includes the optional load-bearing collars, which makes the complete thing more like a real seacock instead of just a ball-valve screwed on top of a through-hull. Perhaps overkill, seeing how the previous brass valves have lasted 15 years without any support, but since there are some pots and pans in that locker that could fly around and since the load bearing collar didn't massively increase the cost, I've opted to go for them.
Only if you do so, you need the packers, depending on your hull thickness where your seacocks are (mine is only 9mm in that area - a bit surprising compared to the 1980s Oyster I've previously fiddled with, but clearly not a problem). The included manual tells you what the minimum hull thickness is and to add packers if too thin. So I needed packers and made them from 20mm HDPE sheet (off-cuts from an
industrial supplier on eBay) - simply cut a disc the diameter of the collar and a hole in the center somewhat larger than the thread of the skin fitting. Then Sika it all together - the manual describes all this, including recommended sealants. The reason I used HDPE instead of plywood is that it will never rot, and these seacocks are meant to last the lifetime of the boat, whatever it may be. Hooray for plastics!
For cutting out the old skin fittings, I've found a Dremel with fibre cutting wheel ideal. If you don't have a used wheel, grind it down on some scrap metal until it fits straight into the skin fitting, then simply cut around the side once.