How can I tell (or can I?) if a through hull needs to be replaced

[basssears]

Trying to figure out if there is a reliable way to tell if through hulls need to be replaced. Mind you, talking about the actual through hull not the valve etc.

There are two gate valves (and one even worse setup) that will need to be replaced on our soon to be new to us 1988 Gulf 32... the question is whether I can simply remove the old valves and use the Groco flanged adapter:
Flanged Adaptors
... lag screwed to the backing plate with a proper in line valve connected to the adapter.

I know this might seem like cutting corners a bit (i.e. lag screws instead of through bolting the flange, and not replacing the whole through hull) but I know from reading these will be a nightmare to get out, and beyond my skill level (the current through hulls are not mushrooms but flush head, glassed into the hull itself... takes major grinding and fiberglass repair to remove:
Stories of Aeolus- Our Gulf 32 Pilothouse: Replaced Thru-Hulls and Seacocks-Down the rabbit hole)

So am I wasting money if I don't replace the through hulls themselves (which, for my skill level, would require yard work by someone who charges lots per hour) or would this be an upgrade worth doing that would last for a few years?

Here are pictures of the two gate valves and the through hull fittings they're attached to... is there a way to determine condition?





Thanks in advance.

-- Bass

[Don C L]

The through-hull looks ok to me as is. Is is leaking? It does not look overly corroded. I am pretty sure you'll be able to get a new valve that goes on the through-hull without an adapter. Is this through-hull in a spot where something might fall on it? Are you concerned about its strength? As it turns out I have to replace a valve and through-hull this weekend, but in my case the through-hull itself is broken and needs to be replaced. I don't see a need for putting in a new one unless it really has a problem. If it MUST have an adapter, then, yes, I'd say get one rather than change out the through-hull.

[basssears]

No leaks as far as I can tell. And regardless of what kind of install I did, even the full ABYC version, I would still keep all heavy things away from my through hulls, just scares me too much.

That being said, if I can I'd like to upgrade the install as much as possible without making a scary big project out of it, I believe the adapter setup on the interior wouldn't be too huge a job for me, as long as I can leave the existing through hull in place.

-- Bass

Originally Posted by Don C L

The through-hull looks ok to me as is. Is is leaking? It does not look overly corroded. I am pretty sure you'll be able to get a new valve that goes on the through-hull without an adapter. Is this through-hull in a spot where something might fall on it? Are you concerned about its strength?

[HopCar]

I think your plan is a big improvement over what you have now. When you've got the valves off, examine the interior of the thru-hull for pitting or cracks. I don't think you'll find any. Do use the Groco flanged adapters to eliminate the thread mismatch. Replace the gate valves with marine ball valves. Groco or Apollo are good brands.
The only real concern I have is that your backing blocks don't look thick enough to accept much of a screw. Give some thought as to how you might improve those.
Groco Flanged Adapter IBVF
Groco Full Flow In-Line Ball Valves (IBV series)
Groco Seacock Backing Block

[capt-couillon]

The gate type valves you now have were not uncommon in the past and since they are threaded directly onto the thru-hull which has a straight thread (vs tapered thread found on standard residential type gate valves) they are most likely bronze sea cocks although not the preferred style.

That being said, your photos (from here anyway) look as if the backing blocks are solid with no signs of leakage so one would assume the bedding is still sound. As you will obviously have the boat on the hill for the seacock project, before removing the existing cocks, give em a serious "yoink" in all directions. If there is ANY movement, re-bed the thru hulls after inspection. More than likely you do have "mushroom" type fittings and knocking them out and re-bedding them is really not a big deal (other than having to get within 10' of 5200)

Unless the thru hull, sea cock combination is exposed to possible impact from heavy objects or getting stepped on, I think the adaptor is overkill. It will require a taller backing block be installed to soak up the interior length of the thru hull and without thru bolts (and their attendant issues) will be no stronger than the bond between the new block and the old.

One last caveat... You will need to borrow (or buy) a step wrench so your partner can hold the thru hull from turning (outside) while you break the existing sea-cock loose inside. If the thru hull turns AT ALL the bedding is now toast and will cause you no end of future problems. Stuff happens, but a judicious application of heat to the sea-cock thru-hull joint usually makes the process easier.

Remember this advice is worth just what you paid for it

[HopCar]

Capt C. I'd bet big money, maybe even as big as a dollar, that those valves have tapered threads screwed onto the straight threads of the thru-hull. I've never seen a gate valve like that that didn't have tapered threads. There is also a very good chance that the stems in those valves are brass which has de-zinced to the point that they will break rather than move the gate.

I really think the OP is on the right track going to something, either flanged adapter or real flanged seacock that eliminates the straight / tapered thread mismatch and supports the thru-hull fitting it self.

[basssears]

Question on this... how on earth do you tell *which* brand through hull it might be and therefore which style step tool you need... they look far from universal...

-- Bass

Originally Posted by capt-couillon

One last caveat... You will need to borrow (or buy) a step wrench so your partner can hold the thru hull from turning (outside) while you break the existing sea-cock loose inside. If the thru hull turns AT ALL the bedding is now toast and will cause you no end of future problems. Stuff happens, but a judicious application of heat to the sea-cock thru-hull joint usually makes the process easier.

[capt-couillon]

@HopCar....
A dollar? I dunno buddy, that's a little rich for my blood.

While you don't see 'em anymore due to the stem problems you referenced, back in the 60s (and before) you did find gate type valves (with NPS threads, not NPT) especially in larger diameters. The Solitaire had a 2" NPS threaded gate on the original thru hull for the head. It was replaced with a std gate type seacock during the refit, but if I hadn't tossed it, I could make myself a rich man

@bassears....
re: step wrench. Depending on your yard, they might let you borrow one, most thru-hulls have a couple of little tits on the inside diameter. I have my own tool which is just a tapered piece of 3/16" steel Put it in the hole and gently tap it into place with a small hammer. Hold with bigger pipe wrench than you are using inside.

Discussion on removing corroded thru-hulls and sea-cocks here:
http://www.cruisersforum.com/forums/...lls-49030.html

[transmitterdan]

Originally Posted by basssears

Question on this... how on earth do you tell *which* brand through hull it might be and therefore which style step tool you need... they look far from universal...

-- Bass

When you look at the through hull from outside you will see 2-4 "grooves" at the inside edge of the hole. This is for the tool that holds the through hull while threading on/off the valve and adapter. You will need a tool that fits these grooves. It is pretty easy to make such a tool or have one made by anyone handy with a welder. Most tools available for purchase are designed to work with the most common sizes.

[GALAWA]

dear all,
I am always impressed by the speed with which relevant and often well documented replies reach a forum as soon as it is initiated.
Joining this forum late I wish to tap your collective wisdom on a related issue:
My boat was built in 1999 and fitted with plastic through hull.
Do you know why this practice appears to have been discontinued ?

[basssears]

Check some of the replies in this and other through hull threads... basically, it depends on what you mean by "plastic" (and for that matter what you mean by "through hull"... there is the through hull fitting that is fitted into the hole in your boat, and then there is the seacock / sea valve that is attached to the through hull fitting, some people mistakenly refer to the seacock / sea valve as the through hull).

As I gather (can't guarantee) sounds like some older boats were built with true plastic through hulls, which was not a good idea... my understanding is while they didn't "corrode" per se, they got brittle and failed. That's a regular sort of "plastic", I believe like PVC.

BUT, people also refer to a particular Forespar product as a "plastic" through hull... that material is actually a material they call "marelon" which is considered perfectly acceptable to this day (there are some small plusses and minuses between bronze and marelon through hull fittings which will be argued endlessly - think monohull vs multihull disucssion- but the point is it's an accepted material to use and if someone sees true marelon through hull fittings they're not going to go "holy god you have to get rid of that right now!")

-- Bass

(PS, since I'm new to this, I will parrot other's comments that my advice is worth exactly what you pay for it.)

Originally Posted by GALAWA

dear all,
I am always impressed by the speed with which relevant and often well documented replies reach a forum as soon as it is initiated.
Joining this forum late I wish to tap your collective wisdom on a related issue:
My boat was built in 1999 and fitted with plastic through hull.
Do you know why this practice appears to have been discontinued ?

[Cadence]

Just as a SWAG, I doubt the bronze through hull is glassed in. At 27 years I would hazard a guess it is replacement time. I assume it is electrolysis but they can get brittle with age. From your pics I would have a concern about the single hose clamp and for that matter that hose type?

[Pedersen]

An easy way to tell if a brass or bronze through hull is dead is to scratch the surface of the fitting. If the scratch shows yellowish the metal is probably ok, however, if it is pinkish in colour, it MUST be replaced because it is corroded and can fail rather easily. I just replaced a through hull that showed pinkish. During the process of knocking it off it simply broke off clean - the bronze was that fragile!
I have attached a photo of the broken fitting. It shows the inside of the fitting (against the hull).
A New Zealand company, "Trudesign" produces valves and through hulls made of a "plastic" composite. They are approved by Lloyds for commercial vessels and are really great, albeit rather bulky. I'm replacing all my valves and through hulls whith these.

[Dougtiff]

I use a PIPE wrench, the right size [handle] works very well also if the Bronze thru-hull is good[scrape down to metal] if it's not Yellow, but Bronze color, i would leave it, as the junk coming out of China[Bronze] is not the quality that was produced here, also Bronze doesn't get brittle, i have pulled Bronze keel bolts that were 50 year's old and as good as the day they were put in.

[Dougtiff]

I should have said PINK instead of Yellow in the scrape test, if PINK it indicates electrolysis.