Pascoe, one of those guys, made up a chart of causes of sinkings - by far the most, more than 50%, were related to seacocks.

In your case, Scott, maybe the Grocos are ok but the pads aren't. IMCO backup pads made of wood or ply, especially ply, unless phenolic marine grade, will degrade after awhile.

Suppose one could make an arguement for a seacock install that has some give in it - wood backup fairing. BUT 338 will have molded epoxy/glass fairing and true three corner seascocks bedded in polysulphide. Giving the thruhull support thru the hull with a thick pad for more rubber bedding I think is good. 338 will have flush thruhulls therefor building up the hull there is called for.

When I get an assembly ready I may even consider dolphinite bedding compound rather than sulphide. Since thruhulls have to be considered a maintenance item, making the whole install relatively easy to take apart would be the way to go. If it wasn't daunting it wouldn't get forgotten. Something like that.

Anyway, doncha love a mystery???