Replacing original 47 yr old thru hulls

[Sirzones]

Started replacing original they hulls on my 1974 C&c mk1 30 footer the other day
Found that the only sealer at the hull was wax, looked just like toilet bowl ring wax
Has anyone ever come across this?
I plan on reinstalling with 3m 4200 marine sealer

[LittleWing77]

Originally Posted by Sirzones

Started replacing original they hulls on my 1974 C&c mk1 30 footer the other day
Found that the only sealer at the hull was wax, looked just like toilet bowl ring wax
Has anyone ever come across this?
I plan on reinstalling with 3m 4200 marine sealer

Who knows what they did back then, eh? You're talking about a 50-year-old boat, after all. I delivered one like that at the beginning of the Summer and the only new thru-hull/seacock was the one for the head. Gave me the heebie-jeebies!

Here's a fantastic resource for replacing thru-hulls/seacocks:

Marine How-To: Replacing Thru-hulls and Seacocks
https://marinehowto.com/replacing-th...-and-seacocks/

Good luck - Prime task for a sailor: keeping the water out!
LittleWing77

[Sailmonkey]

When I changed the seacocks /through hulls on my ‘76 allied the bedding felt like waxy dolphinite.

Worked well for 40 years, and was easy to disassemble

[LittleWing77]

Originally Posted by Sailmonkey

...felt like waxy dolphinite.

Is that a real thing, Sail Monkey?

Not that I disbelieve you!
LittleWing77

[pcmm]

Originally Posted by LittleWing77

Is that a real thing, Sail Monkey?

Not that I disbelieve you!
LittleWing77

Dolphinite has been around for decades. It was often used between keel timbers in wooden boats

https://www.pettitpaint.com/products...ding-compound/

[LittleWing77]

Originally Posted by pcmm

Dolphinite has been around for decades. It was often used between keel timbers in wooden boats

https://www.pettitpaint.com/products...ding-compound/

Wow...!

That's certainly an old compound.

Wild,
LW77

Oh, and thanks PCMM, for the info. What a strange product name, eh? Sounds almost as if it's made-up. Wonder why their marketing dept. landed on "dolphin"-ite.

[pcmm]

Yeah its definitely a strange name for a product. I only know about it because I grew up reading "Wooden boat" magazine!

[Manateeman]

There are two types of Dolphinite. The original product had a fungicide in it but it was removed, I think, because of EPA requirements. Old wood boat builders would use red lead first. Some would mix copper bottom paint into the Dolphinite.
A lot of this can be found in old Wooden Boat articles.
There was another marine mammal label showing a seal beating a drum. I thought it was Seal-Tite but I can’t find the illustration.
Manatees charge exorbitant rates for commercial image use and insist in prepayment to Save The Manatee.org. They’ve had all sorts of offers but are holding out for a major brewery or pizza chain.
Happy trails to you.
Captain Mark

[PerfectPirate]

The substance sealing your old thru-hulls is grey butyl, usually sold in the form of a tape. It is the same substance which seals the multiple layers of the hull-deck joint in all C&C's (also Hinterhoellers (Niagaras & Nonsuches) and Ontario yachts) and, as all owners of those boats can attest, it remains flexible and oozy indefinitely. This is what makes it a superior sealant, as it easily accommodates flexing and movement, and will literally reseal itself if movement should momentarily break the existing seal.


After 37 years of mounting and sealing thru-hulls and deck hardware, I have learned this: anything which I seal with butyl tape stays sealed and never leaks, any other kind of sealant (except possible 5200) will eventually dry out, or yield to UV, or have its seal broken by movement. At this point in my sailing career I bed everything with butyl tape, including the new thru-hulls which I am installing to my classic plastic baby. As a bonus, when you remove a piece of hardware which has been sealed with butyl, you can usually clean it up by simply "rolling off" the old sealant with your fingers. Since it likes to stick to itself, you can clean off threads by using a lump of old sealant to "stick and pick" the remainder out of threads, etc.

[Sirzones]

It is definitely not butyl, it has a honey colour and feels like wax

[PerfectPirate]

Your response is interesting to me, as when I pulled the thru-hulls on my 1980 C&C 27 they were definitely bedded with gray butyl. I do know that butyl does come in different colours, including black and apparently now white, but I have never encountered it in a honey colour.


When I replaced the thru-hulls in my 27 I bedded them with 4200, figuring that they would never be seriously exposed to UV or flexing. Some of them subsequently leaked, which was the final straw in my total conversion to using butyl. I found butyl to be especially effective around chainplates, which are constantly working and shifting where they pass through the deck.

Anyhow, good luck on your project. As I noted earlier, I too am replacing thru-hulls on a 46-year old project boat and, as tasks go, it is a true pain in the ass! Also, the back, shoulders, biceps, etc. What sort of valves will you be installing to the new thru-hulls? Are you converting to true seacocks?

[LittleWing77]

Originally Posted by Manateeman

There was another marine mammal label showing a seal beating a drum. I thought it was Seal-Tite but I can’t find the illustration.

Manatees charge exorbitant rates for commercial image use and insist in prepayment to Save The Manatee.org. They’ve had all sorts of offers but are holding out for a major brewery or pizza chain.
Happy trails to you.
Captain Mark

Pizza chain! Pizza chain!

Hahahahaha!
LittleWing77

[Sirzones]

I’m using bronze thru hulls with brass ball valves
I’ll post a picture off my old thruhull

[PerfectPirate]

I too am using bronze thru-hulls since my old backing plates were not large enough to accommodate proper seacocks and I did not feel like trying to chisel off the old backing plates and fiberglass new ones in while working under the cockpit from the lockers.

However, I have a couple of points of concern, which you may already be aware of. Thru-hulls are manufactured with an NPS (National Pipe Standard) thread, while ball valves are almost universally manufactured with an NPT (National Pipe Tapered) thread. This mismatch of threads means that you will only be able to engage 2 or 3 threads, at most, of the thruhull into the valve, leaving the connection weak and vulnerable. That is one of the reasons that I removed my old valves and chose to go with Marelon ball valves. Marelon valves are manufactured with an NPS thread and will engage a full inch or so of the thruhull's threads into the valve body, making the connection much more secure. I put Marelon valves into my C&C 27 some sixteen years ago and never regretted it.

Also, your profile indicates that you are based on the east coast, presumably in salt water. Using brass valves (rather than bronze) will leave you vulnerable to dezincification of the valve body and components, since the brass is galvanically incompatible with the bronze thruhull. The brass will become very brittle and lose its structural integrity. Marelon valves will also avoid that particular problem. There is an excellent discussion of these issues available at:
https://marinehowto.com/replacing-th...-and-seacocks/

[sailor_ed]

I suspect you are dealing with old silicone sealant. Back when your boat was built silicone was a new miracle sealer and was probably used in lots of inadvisable places...
and still is!


Go with butyl and don't over tighten at first.



Fair winds