Groco seacock

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cardude01

cardude01

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Joined
Nov 26, 2012
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5,290
Location
USA
Vessel Name
Bijou
Vessel Make
2008 Island Packet PY/SP
My AC seacock has some play on the handle before it starts to engage the actual valve. Like maybe 1/8". It's not a loose handle but the actual shaft has play.

Is that a bad sign? Am I gonna sink?

ImageUploadedByTrawler Forum1441837689.631399.jpg
 
I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
 
TDunn said:
I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
Click to expand...


Wow. Really. Wonder if my others are like that? I will go look.
 
Generator has same setup I think.

ImageUploadedByTrawler Forum1441839478.676178.jpg
 
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Main engine inlet. Not a good pic. Seems to be a better setup with bolts?

ImageUploadedByTrawler Forum1441839525.047287.jpg
 
TDunn said:
I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
Click to expand...

:thumb:
 
Generator is also a ball valve on the thru-hull. You have an actual seacock on the main engine intake. I always wonder why builders install ball valves considering the thread mismatch. I guess it is to save a few bucks since a seacock costs 2-3 times what a ball valve costs. It is possible to mount a seacock without a thru-hull, although I always use one.
 
Tdunn is right, replace those with real seacocks next time you haul.
Another option would be to use a Groco flanged adapter between the thru-hull and ball valve.

Is there a backing block or are those mounted directly to the hull? If no backing blocks, add them.
 
HopCar said:
Tdunn is right, replace those with real seacocks next time you haul.
Another option would be to use a Groco flanged adapter between the thru-hull and ball valve.

Is there a backing block or are those mounted directly to the hull? If no backing blocks, add them.
Click to expand...


I think directly to the hull.

This looks like an interesting product.
ImageUploadedByTrawler Forum1441885118.828857.jpg
So if your valve wears out you just screw another one on.

I'm surprised the manufacturer didn't install the better seacocks on this boat for all through hulls. Why would they use them on the main engine inlet but not the gen or AC?
 
TDunn said:
I doubt you will sink, but it sounds like it is time to replace that mess with an actual seacock (i.e., not a thru-hull with an attached ball valve). Remember thru-hulls have straight threads while ball valves generally have tapered threads. That ball valve is likely only engaging 3-5 threads on the thru-hull.
Click to expand...

TDunn said:
Generator is also a ball valve on the thru-hull. You have an actual seacock on the main engine intake. I always wonder why builders install ball valves considering the thread mismatch. I guess it is to save a few bucks since a seacock costs 2-3 times what a ball valve costs. It is possible to mount a seacock without a thru-hull, although I always use one.
Click to expand...


Before the sky actually falls...

I did have some previous discussion with Buck Algonquin about the threads on their seacocks and ball valves... and their tech told me they purposely cut the leading threads so their NPT ball valves will attach securely to an NPS thru hull. Groco literature, somewhere down in the fine print, suggests the same.

Near as I can remember, I've never owned a boat with flanged seacocks. None have sunk, or even leaked.

Not suggesting this is good practice, just adding perspective...

-Chris
 
That first picture is of a marine ball valve. See the drain plug in the lower right- that indicates a marine thru hull ball valve. These valves have straight threads on the bottom to screw in to the straight pipe thread on the thru hull and tapered threads on the top.

As the pbase article indicates this installation isn't the best, integral flanged seacocks are better. But as the previous poster indicated, they rarely fail.

That slop that you feel is normal. There is a stem that fits in to the ball with a socket. It is designed to have a little slop.

David
 
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djmarchand said:
That first picture is of a marine ball valve. See the drain plug in the lower right- that indicates a marine thru hull ball valve. These valves have straight threads on the bottom to screw in to the straight pipe thread on the thru hull and tapered threads on the top. There is nothing wrong with these, but integral flanged seacocks are stronger.

That slop that you feel is normal. There is a stem that fits in to the ball with a socket. It is designed to have a little slop.

David
Click to expand...


Oh. Cool. So not tapered and about to fall off or whatever?

How long do valves like this usually last? And why is the main seacock bonded but not these ball valves?

This makes me think these were added later by a yard and not the factory.
 
ranger42c said:
Before the sky actually falls...

I did have some previous discussion with Buck Algonquin about the threads on their seacocks and ball valves... and their tech told me they purposely cut the leading threads so their NPT ball valves will attach securely to an NPS thru hull. Groco literature, somewhere down in the fine print, suggests the same.

Near as I can remember, I've never owned a boat with flanged seacocks. None have sunk, or even leaked.

Not suggesting this is good practice, just adding perspective...

-Chris
Click to expand...

Yep and hundred's if not thousands of center console boats have that setup and are fine, it's not right but i don't see it as an immediate risk. The Nordhavn has flanged sea cocks, my dusky doesn't as seen far worse abuse and is all fine.
 
According to the technical data sheets at Groco, Buck Algonquin and Apollo their ball valves all have only tapered threads although you can order apollo valves with straight threads. However, if you order straight thread valves, then you have the problem of finding straight thread hose barbs. While those may exist, Groco, Apollo and Buck Algonquin don't sell them.

So if some Buck Algonquin phone guy told you their valves have straight threads on the input end all I can say is that their technical specifications on the web site say the valves are all 100% tapered (NPT) threads.

Even if you can find hybrid thread valves, I would argue that real seacocks are stronger than ball valves every time. Why go with anything but the best?

As I said above, the only reason for a builder to put ball valves onto thru-hulls is to save money. Boat building is a low margin business, so saving $100 per thru-hull adds up. Nevertheless, I would demand actual seacocks.

When I bought my boat the thru-hulls all had ball valves. One of the first things I did before the boat went in the water was to replace all the thru-hulls and valves with seacocks. The original raw water intake on Tortuga had 17 separate plumbing fittings.
 
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Ok. I guess I will add this to my project list. ?

When I change over to actual seacocks should they be bonded? The main engine (probably factory installed) seacock is tied to the binding system.
 
"These valves have straight threads on the bottom to screw in to the straight pipe thread on the thru hull and tapered threads on the top."
Sorry Dave, that's incorrect. Both sides have tapered pipe threads. That's why Groco invented the Flanged Adapter.


"Near as I can remember, I've never owned a boat with flanged seacocks. None have sunk, or even leaked."
Chris, it is actually approved by ABYC to install ball valves directly onto thru-hull fittings because very few of them fail, but some do fail. Over the years I've sold thousands of ball valves and thru-hull fittings. I've only heard of one failure and that was when someone accidentally kicked one and the thru-hull broke below the valve.


Boat builders install them because it is cheap. It is not best practice by any means.

The miss-matched threads are not the only problem. The thru-hulls are very thin at the bottom of the thread and can break. It really doesn't cost much more to do it right. Why not do it right?

Yes they should be bonded. That's another problem with the ball valve on thru-hull, no easy way to connect a wire.
ibvf-correct.jpg

groco-seacock-backing-block-21.jpg
 
Good information, straight thread VS. NPT thread.
I wonder what the cost difference would be between a through hull straight thread fitting and ball valve and a true sea cock would be? I would guess this affects the bottom line and that's why boat builders use them?
I would add that a flanged sea cock without the mechanical screw joint would be stronger. Most failures I have seen with mechanical joints occur at the cut in the threads. One less joint to worry about. I would recommend that you exercise the valve at least twice a year. Don’t worry about the little play if it opens and closes properly. I would also ground it.
Ball valves , sea cock or straight are they best valves to use.
 
So looking at these pictures, can I leave the existing through hull in place and just install the flange and a new valve?

How does that flange bolt to the hull?
 
TDunn said:
So if some Buck Algonquin phone guy told you their valves have straight threads on the input end all I can say is that their technical specifications on the web site say the valves are all 100% tapered (NPT) threads.
Click to expand...


It was during a phone conversation, where I had asked pretty much the same questions... and partly because of the specs on their website.

He didn't say their valves have straight threads, though; he said their NPS thru-hull threads are "slightly modified" to work better with NPT ball valves. (Backwards from the way I said it before; sorry, just re-read my notes from back then.)

This from a note I posted (on another forum) shortly afterwards (11/7/2011):

Another tidbit I just learned today...

The very helpful sales assistant at Buck Algonquin told me they've machined the NPS threads on their thru-hulls in a way that allows them to accept an NPT-threaded ball valve. He said to expect approximately 3 turns before the threads lock up, with Teflon tape recommended as the pipe sealer.

He also said he thinks all thru-hull manufacturers do the same -- and that seems to jive with what Groco describes as "combination threads" on the ends of their NPS-threaded through-hulls.
​
At the time I thought it made absolutely no sense at all for companies to make ball valves with NPT threads intended to mate up with NPS thru-hulls. Since then I've come to suspect they assume their marine ball valves will be used in a number of different applications where NPT threads would be appropriate... and have maybe adopted this kind of approach simply because ONE of those applications (probably relatively low volume, marine thru-hulls) would mean mating NPT-NPS threads. IOW, cost control for the manufacturers, too, not just the boat builders.


-Chris
 
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cardude01 said:
So looking at these pictures, can I leave the existing through hull in place and just install the flange and a new valve?

How does that flange bolt to the hull?
Click to expand...

You will have to remove the nut that holds the thru-hull into the hull. The thru-hulls screw directly into the seacock. Depending on the thickness of your hull it may be necessary to cut the length of the thru-hull down so that the seacock will fit all the way down on the thru-hull. As far as attaching the seacock to the hull there are several options. The easiest is to through bolt them using bronze flat head machine screws. Some people install a comparatively thick backing plate to the hull then drill and tap into the plate for bronze machine screws or bolts. If you do that be sure to epoxy the backing plates to the inside of the hull.

Another consideration is coring in the hull. If your hull is cored, the core should be removed where the seacock goes and that area built up with solid fiberglass, ideally to the thickness of the cored hull. This will strengthen the seacock attachment point and minimize the possibility of water getting into the core. A good builder will have already done this.

Personally, I would replace the thru-hulls at the same time that I did the seacock install. Thru-hulls are cheap.
 
cardude01 said:
So looking at these pictures, can I leave the existing through hull in place and just install the flange and a new valve?

How does that flange bolt to the hull?
Click to expand...


I think you can safely do nothing... until/unless you begin to see some sign of failure down the road, maybe 10-15-20 years from now. Sluggish rotation, for example...

Always good to get things "more perfect" of course, but if you've got other stuff to deal with -- things not actually working, for example -- it should be easy enough to establish reasonable priorities that don't cost you an arm and a leg replacing immediately serviceable stuff.

IMO, of course...

-Chris
 
Cardude, I suggest that you use the Groco premade backing plates and the Groco flanged adapters. Inspect and clean your existing ball valves and thru-hull fittings. if they look ok, reuse them.

The backing plates are usually glued to the hull with epoxy. they have threaded inserts to which the flange is bolted.

Chris, the only combination threads I've seen were on a stainless thru-hull and I can't remember who made it. I read Groco's instructions for installing Seacocks and In-line valves on thru-hulls. (with flange it's a seacock, without flange it's an inline valve). The instructions do talk about combination threads but I don't think Groco (or Buck) thru-hulls have combination threads. I'll ask Groco about it and let you know what I find out.

The thru-hull that I saw with combination thread had a definite taper over about the last inch of thread. It was very obvious.
 
HopCar said:
Chris, the only combination threads I've seen were on a stainless thru-hull and I can't remember who made it. I read Groco's instructions for installing Seacocks and In-line valves on thru-hulls. (with flange it's a seacock, without flange it's an inline valve). The instructions do talk about combination threads but I don't think Groco (or Buck) thru-hulls have combination threads. I'll ask Groco about it and let you know what I find out.
Click to expand...


Sounded nuts, to me, but then I have no clue about what manufacturing costs would be for two different lines of ball valves, one with NPS for use with thru-hulls, and one with NPT for use most everywhere else.

And apparently ball-valve/thru-hull installations are ubiquitous.

-Chris
 
HopCar said:
Cardude, I suggest that you use the Groco premade backing plates and the Groco flanged adapters. Inspect and clean your existing ball valves and thru-hull fittings. if they look ok, reuse them.

The backing plates are usually glued to the hull with epoxy. they have threaded inserts to which the flange is bolted.
Click to expand...


I relapped the old tapered cone valves during a haulout past winter and ended up replacing one "incorrect" through hull and valve and went with the backing plate and setup as Parks is suggesting. Thickened West to secure the backing plate. This made for a very robust set-up. I posted pics of the process on a thread at that time. I was encouraged to grind the existing mushroom head off on the outer hull- since unscrewing ANYTHING with NPT and NPS joined together is challenging.
It worked like a champ.



Forky
1983 Present 42 Sundeck
Twin Lehman 135's
✌️
 
I just replaced 13 below-the-waterline through hulls and seacocks on our boat (not all pictured below). Not a trivial job, but very straightforward if you follow the excellent step-by-step directions from Compass Marine (as previously posted). I used the Groco flanged adapters and backing plates epoxied to the hull. Great quality equipment and the installation is many times more robust than the original. I bought all the gear from Parks, whose prices were unbeatable.





img_368249_2_38ef749834ce2cbbaa34c808a5289927.jpg
[/URL
 
Wow. That's a lot of through hulls!
 
HopCar said:
Cardude, I suggest that you use the Groco premade backing plates and the Groco flanged adapters. Inspect and clean your existing ball valves and thru-hull fittings. if they look ok, reuse them.

The backing plates are usually glued to the hull with epoxy. they have threaded inserts to which the flange is bolted.

Chris, the only combination threads I've seen were on a stainless thru-hull and I can't remember who made it. I read Groco's instructions for installing Seacocks and In-line valves on thru-hulls. (with flange it's a seacock, without flange it's an inline valve). The instructions do talk about combination threads but I don't think Groco (or Buck) thru-hulls have combination threads. I'll ask Groco about it and let you know what I find out.

The thru-hull that I saw with combination thread had a definite taper over about the last inch of thread. It was very obvious.
Click to expand...


OK. I get it now. I think I will tackle this project down the road during my next haul out.
 
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