Re-bedding a Thru-hull - how big a deal?

[Terra Nova]

5200 is the proven sealant for thru-hulls. I use Leak Lock on the threads and 5200 on the flanges and hull.

[skipmac]

Originally Posted by Terra Nova

5200 is the proven sealant for thru-hulls. I use Leak Lock on the threads and 5200 on the flanges and hull.

No doubt 5200 will seal a thru hull but there are a number of other products that will bed and seal a thru hull just as well and will be removable if you ever need to work on it.

5200 works very, very well don't it on anything that there is even the slightest chance it will ever need to be removed for any reason.

[Bleemus]

From MaineSails excellent series on through hulls . . .

"So why do I use Sikaflex sealants or bedding compounds rather than 3M products? That's an easy one for me to answer. In my experience I've found it less aggressive in it's adhering properties than 5200, something I really like for future repairs. I've had vast amounts of experience, over 30+ years, with many marine sealants and have really grown to like the Sikaflex products.

If there is one thing I've learned, in 30+ years of boating, it's that NOTHING on a boat is permanent, not even a keel joint, so there is absolutely NO need for a sealant as permanent as 5200. In my opinion 3M 5200 was invented to ensure future boatyard revenue but remember what my opinion is worth.

I've seen 5200 destroy gelcoat, port lights, hatches and teak among other things. There is only one product not allowed on my boat and it's 3M 5200. 3M 4200 was a move in the right direction, being less adhesive than 5200, but for many projects it's highly adhesive properties are still not necessary and it's still overly tenacious in it's grip.*

Now don't get me wrong I'm not saying, in any way, that Sikaflex comes apart like butter, it does not, but it comes apart easier 5200. Try Sikaflex 291 & you'll like it's adhesion, flexibility and long life."

http://www.pbase.com/mainecruising/r...ruhulls&page=2

[sagablu]

Originally Posted by bobnlesley

After the first couple of seacocks that I ever replaced, I now just replace the thru-hulls too as a matter of course. Having disconnected the hose (cut it off if it's tight) I don't even bother trying to unscrew anything, just carefully apply an angle-grinder/disc-cutter to the outside flange then knock the whole unit inwards; I know that I tend to work slowly/methodically, but if the parts/tools are to hand, I'd still expect to be done and dusted within 90 minutes, provided that there's no issue with the hole itself.

An easier way to remove stubborn thru hulls. Hammer in a soft wooden plug from the outside and then cut off flush. Then drill out the flange with a hole saw slightly larger than the inside diameter of the hole. 5 min job, clean and hard to damage the surrounding hull.

[Terra Nova]

Originally Posted by skipmac

...5200 works very, very well don't it on anything that there is even the slightest chance it will ever need to be removed for any reason.

Not true.

There is a de-bonder readily available for 5200.

[Opie91]

Originally Posted by Terra Nova

Not true.

There is a de-bonder readily available for 5200.

Carefully applied heat to the thru hull will de-bond 5200 also. CAREFULLY! Don't go crazy, it doesn't take that much.

[skipmac]

Originally Posted by Terra Nova

Not true.

There is a de-bonder readily available for 5200.

Have a bottle and it works sometimes. Other times, especially really old 5200 not so well. Also not sure how I can soak 5200 with the debonder when the 5200 is an inch or two under the edge of a flange or similar so only a tiny edge is exposed.

Have also tried heat with limited success.

However, even if heat or debonder will, with some hassle, remove things bedded with 5200 why not use something else that beds and seals just as well but is removable without the extra hassle of 5200?

[Terra Nova]

Originally Posted by skipmac

...why not use something else that beds and seals just as well...

Simple--there isn't.

Thru-hull fittings are among the boat's parts you least likely want to come loose or leak.

[SVRocinante]

Originally Posted by Djarraluda

...Just to be radical, I will note you refer to the sink drain.
Sink drains should be on the waterline, semi submerged at best, so....

Great thought Roger, but unfortunately, mine is just to starboard of the centerline... as far below water as you can get!

[skipmac]

Originally Posted by Terra Nova

Simple--there isn't.

I guess we will have to disagree on this. Based on my experience (and apparently also the experience of others that have years of professional boat maintenance) there are other products that will form a permanent seal that is just as good, just as safe, long lasting and reliable as 5200, without the difficulty of future removal.

Originally Posted by Terra Nova

Thru-hull fittings are among the boat's parts you least likely want to come loose or leak.

There is no argument here. However, a through hull mushroom doesn't need an adhesive (which 5200 is) since it is secured on the inside of the hull with a nut or threaded flange. A good, waterproof, permanent sealant is all that's necessary.