Seacock with Mounting Flange

triton318 · Post by **triton318** » Fri Oct 03, 2008 1:49 pm

I'm embarrassed to ask...I suppose it serves me right for not doing a little research to find the answer.

When you have a seacock with a mounting flange, I know you should first glass in a back plate on the inside of the hull. And I understand the thru-hull threads into the bottom of the seacock. But, are you supposed to bolt the flange through the hull? If so, should you use carriage bolts so you don't have a big ol' bolt head sticking out? And now you've introduced three (or four) new holes to seal?

Or...are you supposed to use wood screws and screw the flange into the wooden backing plate?

Eight years ago, for the head instake and discharge, I installed marelon thru-hull fittings with male threaded ends and then installed Forespar marelon seacocks (or maybe, more correctly, ball valves) onto them. My concern is that, although I know the marelon ball valves are strong, they are relying in part on the strength of the threaded stem of the thru-hull fitting.

So, I'm thinking of replacing them with the flanged type marelon seacocks.

Thanks.

Jay

Post by **Tim** » Fri Oct 03, 2008 1:59 pm

Use flat head bolts, and mill a countersink in the hull so that the heads sit flush.

Case · Post by **Case** » Fri Oct 03, 2008 3:17 pm

Jay -

Tim's way is best.

But there is another way you can install seacocks: Epoxy fiberglass plates (at least 1/2" thick, thicker is better) to the desired area then drill thru the entire plate and hull for the thru hull. For the mounting areas, drill only to the depth of the fiberglass plates then tap it for machine screws. This is how I did it myself - the fiberglass skins was way too thin on my Sea Sprite 23. It turned out to be very solid and I'm pleased with how things turned out. I used Groco ball valves, the pricey one with stainless steel bits - chose it because it was the only ball valve to fit in the tight spot it went to.

Using wood screws and wood plates are so-so - I think they're best for wooden boats... Wood eventually rots and expands so better stick with solid fiberglass only.

- Case

triton318 · Post by **triton318** » Fri Oct 03, 2008 6:35 pm

Thanks!

Rachel · Post by **Rachel** » Sat Oct 04, 2008 2:22 am

I would add that if you use Case's method, and you want a more "bombproof" install (not that his way is weak), you could fiberglass the blocks in place before you install the tapped fasteners. By that I mean to fillet around the edges of the backing block, then put a piece of biax or the like over it and extending out some inches onto the prepped hull.

Rachel

Peter · Post by **Peter** » Sat Oct 04, 2008 10:21 pm

Just a reminder on Groco Seacocks with SS ball shafts: There is a recall notice on some of them covered by this thread

I got mine all changed out, with much help from a fellow sailor, between tides on my beaching legs.

PS: I used the mounting method described by Tim. Works very well!

MikeD · Post by **MikeD** » Sun Oct 05, 2008 9:51 am

Peter, do you have any pictures of your beaching legs in action?

Peter · Post by **Peter** » Sun Oct 05, 2008 11:17 pm

Mike,
I have a few pictures here when I changed props.
I didn't get any while doing the sea cocks, as I was pressed for time. I also managed to park over a hole on the starboard side leg, and had to run out a kedge anchor attached to the main halyard to keep the boat upright. I was amazed at the holding power of a 15lb Bruce! The marks in the mud at low tide showed it had dragged about 1 foot before burying itself securely.

The Froon · Post by **The Froon** » Mon Oct 06, 2008 9:41 am

Peter,

That beaching process is pretty amazing...can you give some more detail on how you perform this? - first time you attempted this, what type of bottom you must ground on, etc...

Thanks,

Brian

Peter · Post by **Peter** » Mon Oct 06, 2008 12:45 pm

Brian,
I'll post a reply under "Projects->Beaching Legs, as it's a bit off topic for this thread.

Idon84 · Post by **Idon84** » Mon Oct 06, 2008 1:17 pm

Nice & Salty Peter!!!