Groco SV Seacock Testing Prior to Installation

[Cheechako]

Originally Posted by endoftheroad

Gotta love MaineSail's work.
Here is a stress test of the Groco Tri flange valves.

I'm considering the flanged adapter/ball valve system.

Also I'm considering not thru bolting the 3 bolts through the hull and only tapping into fiberglass backing blocks. The single thruhull penetration seems sufficient. In addition to the backing blocks being epoxied to the hull.

Any comments?

Yeah, I wouldnt drill and bolt seacocks if putting them in either. I think it's a procedure left over from wooden boats. The last thing I want is a hole in my boat surrounded by three other holes nearby. The flanged base as well as the sealant seem to provide plenty of support. Far better than many boats with simply a threaded thru hull with a valve screwed on.
I think the answer to your question, as mentioned above, is in looking at the condition of yor existing seacocks. I'm not familiar with a seacock with a rubber surface in it... but it sounds like a bad idea to me. However, if they look in decent shape, have you considered using lanolin on the rubber surface? It will often stop leaks and is a bit of a lubricant.
I'm a huge fan of the traditional tapered bronze seacock design. However as mentioned a plain valve can last a long time... yes even gate valves. I've seen production boats with the original gate valves simply screwed on to a thru hull that are 40+ years old..... not that that is a good thing! A tapere bronze valve should outlast the life of the boat... there's really nothing that can go wrong with them that cant be fixed!

[endoftheroad]

I have decided to use Groco's flange/ball valve system.

I was sold on them for my boat a couple years ago but somehow got on the idea of re-using my traditional valves.


Use GPO-3 or G-10 for backing plates.

Check out Maine Sail's detailed "How To" article for the alternate backing block no thu hull-bolting, it's a great read.

Seacock Backing Plates / Alternate Method / No Through Bolts Photo Gallery by Compass Marine at pbase.com

Thanks Maine Sail.

endoftheroad

[endoftheroad]

What shape backing plate do you think would be better for Groco's seacock flange?
I'm leaning towards the circle.
I need to make 8 of them, six 1-1/2", and two 3/4" thru-hulls.

The circles could be cut with a 6 inch hole saw and the triangles would be a ban saw or something.

I know this is overkill to be asking this question but one of these shapes is stronger than the other and I may as well make the better choice.

Circle?
Triangle?

Thanks,
endoftheroad

[HopCar]

I'd go with the circle if you've got a large hole saw. It would spread the load more and the pilot hole lets you center the smaller hole saw to make the cut for the thru-hull in the exact center.

[endoftheroad]

Thanks Hopcar

I have an order for you in the very near future,
You have a nice selection and have most of what I need for this project.

Cheers,
endoftheroad in Key West.

[casual]

Replaced my old Groco Seacocks after 30 plus years. The rubber was ridged and no longer round. They did not leak but required excessive force to close. Replaced with Groco Sea Cocks and Groco Flange's thru bolted to G 10 fiberglass board countersunk the bolts on the underside and secured with nut's on top. No I did not use 5200 to bed. Sikaflex instead. Hop Car gave me the best deal and SERVICE.

[HopCar]

Thanks Endoftheroad and Casual! If you need something you don't see on my website, please just ask. We're still building the website and don't have everything up yet.

[Cheechako]

I'd just band saw circles....

[Badsanta]

Where do you get the thick fiberglass backers?

[Rhapsody-NS27]

endoftheroad,

The picture you posted looked like a Spartan seacock that I've seen on other boats. Your's looks about the same and doesn't look too bad to maintain. If you wanted something that looks like the same type, it might be something to consider too.

I replaced a raw water seacock with a Groco Flange adapter setup using Maine Sails instructions. Much easier than I expected. I got the fiberglass board from Jamestown Distributors. I used a couple hole saws to cut out the shapes. Seemed easier than trying to cut out the triangular shapes I've seen. Like Casual said he did, I used Sikaflex 291 on the flange and thru-hull.

Here is the posts I made for my project:
Rhapsody: Raw Water Seacock, Installed!
Rhapsody: Seacock Project - Complete

I plan on hauling my boat out later next year and put it back on its trailer (for an upcoming move for work) and will do a refit over a few years. I plan on replacing the seacocks the same way I did the first one. Everything was much easier than I expected.

[endoftheroad]

Originally Posted by Rhapsody-NS27

endoftheroad,

The picture you posted looked like a Spartan seacock that I've seen on other boats. Your's looks about the same and doesn't look too bad to maintain. If you wanted something that looks like the same type, it might be something to consider too.

I replaced a raw water seacock with a Groco Flange adapter setup using Maine Sails instructions. Much easier than I expected. I got the fiberglass board from Jamestown Distributors. I used a couple hole saws to cut out the shapes. Seemed easier than trying to cut out the triangular shapes I've seen. Like Casual said he did, I used Sikaflex 291 on the flange and thru-hull.

Here is the posts I made for my project:
Rhapsody: Raw Water Seacock, Installed!
Rhapsody: Seacock Project - Complete

I plan on hauling my boat out later next year and put it back on its trailer (for an upcoming move for work) and will do a refit over a few years. I plan on replacing the seacocks the same way I did the first one. Everything was much easier than I expected.

Rhapsody,
Thanks for the link to the G-10.

Is that stuff $200?

[HopCar]

I've been trying to figure out how to buy it so I could sell it in my store. I haven't figured it out yet. Right now if I was installing seacocks, I'd buy some GPO-3 from Online Metals.
They only stock it up to half inch thick, but if you need it thicker, you could glue two pieces together. If you're careful, you should be able to get four 6" backing plates from a 12 X 12 piece.
Order Plastic GPO-3 Plate in Small Quantities at OnlineMetals.com

[endoftheroad]

Anyone have a source for the 5/8"?

Main Sail?

[Rhapsody-NS27]

Try McMaster Carr McMaster-Carr

It does cost a lot. Going with a full sheet, I have plenty for the rest of the seacocks I plan on replacing. At the time I bought it, it was actually better priced at JD than other places I was trying to find it at, for the amount I needed.

[NahanniV]

G-10 is really overkill ! It is very expensive, hard to work, and I found it difficult to source. I'm not sure what the point of using something that is stronger than the hull ?

There are other options:

Marine plywood painted or epoxied, also very expensive, but you might find some scraps to use for free. even unsealed this stuff can last for 30+ years. Some people say that the softness of the wood is an advantage in that it can absorb some movement of the seacock.

Made up fiberglass. Use cheap woven roving and cloth plus cheap resin to make up sheet. lay it up on a waxed sheet of glass with another piece of glass on top to compress it.

Phenolic (grade C or CE). This stuff is readily available, water-resistant and easy to work with (like wood). I got some for less than a quarter of the price of G-10 and they had it in stock locally. This is the stuff that was used for the cheeks of old blocks called Tufnel(?).

Don't be tempted to use plastic like UHMWPE, sealants will not stick to them.

Cheers,
JM.