Best Bedding Compound for Thru-Hull Fitting?
- Thread starter BrianW
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For nylon you can use a polyurethane such as 3M 4200, Sikaflex 291 or Sikaflex 295 UV. You could also use a polyether like 3M UV 4000. If these fittings ever have the potential to dip below water under power or sail you might consider bronze, stainless or Marelon. Nylon does not like long term UV exposure. The UV inhinhibitors in Marelon seem to do better than standard nylon...
One comment for thru hulls above the water line is the possibility of being submerged if heeled over too much depending on the height of placement above the water line.
There are many compounds but for a permanent one, the use of 5200 has been always recommended. 4200 is a fast cure but not permanent and any adverse jarring, I have seen 4200 actually break their seal but it is above the water line and that would be fine. I have strictly used 5200 for attachement on the hull which has a curing of 7 days. Berlow the water line, stick with 5200.
crazy dave
There are many compounds but for a permanent one, the use of 5200 has been always recommended. 4200 is a fast cure but not permanent and any adverse jarring, I have seen 4200 actually break their seal but it is above the water line and that would be fine. I have strictly used 5200 for attachement on the hull which has a curing of 7 days. Berlow the water line, stick with 5200.
crazy dave
Dave, one of our respected contributors has called 5200 Satan's Glue and suggests it should not be sold to unwary boaters. I agree. Would you not face major difficulties if you ever needed to replace the thru hull? I believe that 5200 should only be used in the hull to deck joint - after all that is rarely something that needs to be replaced.
I completely endorse Stu's views having needed to almost destroy an echo sounder transducer that hunters had 'sealed' in place with 5200.
Much rather risk a small weep in the event of a minor incident than to need to hack the boat to get the fitting out.
Much rather risk a small weep in the event of a minor incident than to need to hack the boat to get the fitting out.
“DeBond Marine Formula” is a 5200 debonding agent. Although I haven't used this product myself it has been well written up. I also believe 5200 should be used sparingly and both 4200 and Sikaflex are in my toolbox.
I replaced the above water line thru hulls on my Hunter 31 just this summer using the nylon fittings and Sikaflex. A very easy job, which I know with the UV exposure, will need redoing in another 10 years or so!
I replaced the above water line thru hulls on my Hunter 31 just this summer using the nylon fittings and Sikaflex. A very easy job, which I know with the UV exposure, will need redoing in another 10 years or so!
Great for deck hardware but I don't use it for thru-hull fittings. The compression of the butyl with a nylon thru-hull can be enough to strip the plastic threads if you did not do it very carefully. Could it work? Sure but I do prefer PU sealant here....
Is that sink discharge factory? Usually gray water discharge is kept bellow the water line to prevent the hull from getting stained.
They use butyl rubber to seal underwater wires and pipelines so I guess it "could" be done. I however have not tested it and do not personally condone it, at least with my product. This is only because I have not satisfied my own curiosity and put it through the paces in that application. With a proper flanged seacock it could work but I still prefer a marine sealant for that application. For an in-line valve slapped onto a thru-hull you actually want the glue properties of a PU sealant as this is already a Rube Goldberg installation...
Below the water line should a thru hull come loose, needless to say the boat will sink once the battery is drained down to a point the bilge point no longers work. Why? I have seen 4200, butyl rubber, silicon and other good compounds but they are not permanent. I have helped many times over the years to bring up boats from the bonnie blue and one reason was due to a loose thru hull leaking below the water line due to jariring from inside i.e. loose heavy gear or being hit from underneath. Not once in over 30 years did I have that issue with any thru hulls embedded with 5200.
I applied liberally and once installedl, cleaned up all the excess either using acetone or alchol and allowing to dry for 7 days. I hope this explains my reasoning for 5200 as it needs to be permanent.
As for removal, there is a debonder as previously mentioned but never used it. I simply took a fine putty knife to cut the seal with and never had issues.
crazy dave condon
I applied liberally and once installedl, cleaned up all the excess either using acetone or alchol and allowing to dry for 7 days. I hope this explains my reasoning for 5200 as it needs to be permanent.
As for removal, there is a debonder as previously mentioned but never used it. I simply took a fine putty knife to cut the seal with and never had issues.
crazy dave condon
The troulble with forums is you can get bad information from people who don't know what they are talking about. 3M 5200 is an ADHESIVE caulk that is very strong and should only be used on permanent bonding situations. I would stick to the old reliable underwater compound called polysulfide caulk. Boat Life makes Life Calk (that is the correct spelling) and it is perfect for underwater applications. As a matter of fact, you can use it and submerge the boat immediately and it will cure quicker with the absence of oxygen (under water). If you like Mother Mining products, then use 3M's 101, but I like Life Calk better myself, because it flows better. Do not use an adhesive caulk. One day you might need to remove the through hull and you will be swearing like a sailor for using that type of caulk. Trust me.
Neither is 5200 "permanent". I think everyone on this forum has had a 5200 failure and is why so many folks hate it. When, not "if" it leaks it is a PITA to remove. I have even had to rebed a failed keel hull joint originally done with 5200. Still stuck like it was welded in many places but not in the area of failure. Would have been a LOT easier and saved an entire day and a half of labor had it been done with a polysulfide or low adhesion PU.
Sadly 5200 in this application is a Band-Aid to a seacock that potentially never met industry standards to begin with. 3M 5200 is a Rube Goldberg fix for a Rub Goldberg installation. 3M 5200 on a seacock is like using Fix-A-Flat to "fix" a flat tire. It's not a fix it's just a Band-Aid attempting to hide a problem not fixed correctly.
With "proper" seacocks a polysulfide works tremendously well even at just 130 PSI bond strength. Never once had one leak, ever. I have many customers with Cape Dory boats and "proper" seacocks bedded with polysulfide going on 30+ years. I am currently working on a mid 80's Ericson with Marelon that was bedded with polysulfide. No leaks even though it's an improper installation.
Alcohol should not be used on 5200 for prep or clean up! Toulene or Acetone are fine.
From 3M:
Limitations -
- Alcohol should not be used in preparation for bonding as it will stop the curing process, causing the adhesive to fail..
Note that this is one of the only red ink warnings on the 3M 5200 TDS....
With an in-line valve slapped on a thru-hull, which does not meet ABYC standards in most sizes, 5200 can be a decent option but it is still in no way "permanent". 4200 can also be a good option. 5200 can be a pain in the arse to remove and because no seacocks is ever a "permanent" installation I generally prefer a product like 4200.. I would suggest that if you need more than the 300 PSI bond strength of 4200 then something is terribly wrong with the installation. Silicone should not be used below water..
De-Bond works but is very time consuming. When 5200 has been used a 4" angle grinder usually works to grind the external head off. For flush mounted thru-hulls some heat and a pipe wrench can break it free. The real pita is getting the internal nut off if someone got 5200 on it..
The bottom line is that if you "need" 5200 then the seacock is not a proper installation and some consideration should be given to doing the job the right way. A seacock installed properly can use the lowest adhesion polyurethane or polysulfide and can still last for 20 or more years. When you take it apart in the future the pars can often be re-used where with 5200 the parts are very often destroyed.
Watched a boat yard last spring ruin some ports on a Niagara 35. The 3M 5200 failed, as in NOT PERMANENT, and most of the ports had to be destroyed to remove them. A week with De-Bond, and over $100.00 spent on the product was of no help for the eight+ ports. the yard tried to salvage the ports but at some point the labor becomes more expensive than the product you are attempting to save. Because 3M 5200 was used it cost the over $2200.00 in new port lights instead of cleaning and re-installing the used ones plus all the added labor in removal. There are 1000's of stories like this that involve 5200....:neutral:
To those who know me, I base what I have done over the years of experience, work, innovative designs and so forth. We can agree to disagree but if properly used with the curing time, 5200 3M worked very well and I never had any customers come back to advise failure in over 30 plus years where I applied 5200 to seacocks below the water line and I installed many. When any thru hull goes on, I overcaulked to let it ooze out without allowing any seacock to turn or that would break a seal. I preferred a sealant that would tenanciously hold below the water line. I have worked with 4200 and polysulfides and still my choice is 5200. Yes it is difficult to take off if embedded with 5200 but at least that seal lasted for many years.
When cleaning, some are affected by the use of acetone which is why alcohol is suggested. Remember, this is for cleaning the excess without getting to the area of the sealant.
crazy dave
When cleaning, some are affected by the use of acetone which is why alcohol is suggested. Remember, this is for cleaning the excess without getting to the area of the sealant.
crazy dave
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