Sealing through hull fittings

[Freedom77]

Well it's my turn to ask questions. Freedom is 42 years old. Everything, including me, dries out in the desert. I think I need to seal/caulk through hull fittings. Someone mentioned something call Butyl tape? Any suggestions.

 

[Jim26m]

I used 3m 4200 to install mine. Supposed to allow future disassembly. Only been in service a couple of years, but so far, so good.
Many of my boating buddies swear by it.

I see butyl tape recommended a lot for deck hardware. Maybe someone else here has used it below the waterline.

 

[Rowlando]

I got Marinesails butyl tape.......very good quality! Although I haven’t used it below the water line I would certainly do so with confidence. Don’t get a “bargain” butyl tape......some dry out rather quickly.

 

[seadaddler]

I used 5200 on thru hulls and that is what Airmar transducers said to use and anything below water needs 5200 and that’s what Hunter uses.
And I did use 5200 when I changed my speed and depth transducers before redoing new
backing plates and change 2 bad thru hulls for my engine and Gen intakes thru hulls.
Nick

 

[Rowlando]

I’ve have zero experience with 5200 but based on all the happy users it may be the more obvious and better choice. My sailing is all fresh water day trips several time yearly with the boat on the trailer otherwise so my knowledge is limited.......in more ways than one............;^)

 

[jamieFL]

3M 4200 is rated to be used below the waterline. 4200 seals as well as 5200,but is not permanent. I think 4000 is the UV stable version of 4200...not needed below the waterline, but great where the sun does shine.

 

[Ward H]

Butyl tape is not meant for under water use. Great for sealing deck fittings and such.
Under water 3M 4200 or Sik-I-Flex 291 are popular. 3M 5200 is also suitable but is considered an aggressive adhesive and considered permanent. Many do not use it on fittings that may need to be serviced as it can damage gelcoat when trying to remove something installed with it.

 

[BigEasy]

I have used 3M 4200 for years, never had a problem with it leaking and it allows relatively easy disassembly if necessary. In my opinion 5200 is an overkill for thru hull fittings; it is rated more as a permanent adhesive for applications such as hull/joints that are not to be dissasembled. Butyl tape should only be used on above water applications where compressive forces will cause the tape to fill voids.