Installing Trudesign seacocks

[vladkri]

Greetings,

Just went over some discussions on subject of seacock installation. OK, those Trudesigns are ball valves, I get it. The question still is what do I use for sealing? There are 3 connections to make: a) the skin fitting aka thruhull to the hull, b) thruhull to ball valve and c) ball valve to barb hose connector aka adaptor. The manufacturer recommends 5200 or 4200 or some other stuff which is no longer produced. For the a) I think 4200 will do, how about Sika 291? For the other two I'm reluctant to use 4200 because I feel it will be impossible to take apart if needed. I used RectorSeal Blue on HWPDE plastic black water tank to seal threaded connections, seems working fine i.e. sealing out liquids while not getting rock hard. Furthermore, when 4200 is used, even if connection is taken apart, it will be impossible to clean out old sealant and this feature is kind of useless. Being a "pipe dope" Rectorseal can probably be removed by a solvent and some parts can be re-used.
Some Youtubers just used 5200 on all three connections.

Thanks in advance.

[pcmm]

4200 is not as bad as 5200. 4200 is more os a sealant than an adhesive. I use Sika 291 on all my thruhulls, but I use bronze

[Belliure 50]

Ill be doing my own thruhulls come February, i plan on using Sika 295 as recommended to me by a local and trustworthy boat maintenance professional. 291 would also do the job.


The sealant is for sealing, the threaded parts and nut, collar etc are the strength. You don't need to add strength with 4200/5200 mega adhesives.

[pcmm]

Originally Posted by Belliure 50

Ill be doing my own thruhulls come February, i plan on using Sika 295 as recommended to me by a local and trustworthy boat maintenance professional. 291 would also do the job.


The sealant is for sealing, the threaded parts and nut, collar etc are the strength. You don't need to add strength with 4200/5200 mega adhesives.

You might want to question why your "trusted boat maintenance professional" is using glass glazing/bonding compound as thruhull sealant??? It's meant for bonding glass to other subrtrates and it has UV stabilizers in it. It will work but 291 is the better choice here.

[Dogscout]

I did all my thru hulls and sea cocks with Tru-Design and Sika 291. Its only been 3 months but no problems so far.

[Winf]

Go to the source, what manufacturer recommends.

We used 291 for a), b) and c) as recommended by Truedesign. No issues so far but only 3 months.

[vladkri]

Originally Posted by Winf

Go to the source, what manufacturer recommends.

We used 291 for a), b) and c) as recommended by Truedesign. No issues so far but only 3 months.

I'm sure there are no issues. The question is if you ever can take it apart. The only purpose of this effort would be fix/change something and re-use some or preferably all parts. Think of changing hose direction or broken handle. Otherwise you would simply cut the whole thing out and use new components. I do think 4200 can be taken apart, but will not allow for re-use.

[Winf]

Have taken other non Truedesign seacocks with 291 apart as with other fittings sealed/adhered with 291- no major issues but guess we will see.

No personal experience with 4200. Side by side compare of the tech specs indicates the 291 has higher tensile strength (1.8 vs 1.4MPa) and higher elongation at break (500 vs 400%) so likely to be tougher than 4200 to take apart. My bet is both probably just fine. Manuf says they have tested with both.

This is what Truedesign say rather than internet forum:

https://trudesignplastics-com.s3.ama...694a665247.pdf

FWIW I now exclusively use bed-it butyl tape for pretty much all sealing above the waterline these days. Thank you Mainsail for showing me the light.

https://marinehowto.com/bed-it-tape/