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Opinions on sealant for through hulls

JPS27

Member III
I'm replacing a few through hulls. Haven't done this before and have been reading different sites. I'd like to know what folks here think about the best sealant for the through hull to the hull and then backing block to the hull and the flange to the backing block. I confess I'd rather not mess with epoxy if something right out of a tube works as well. Depending on what you read epoxy as described by mainsail site, 5200, 4200, lifecaulk, sikaflex 291 oe 292. Would like to hear what the preferences are here and why. Thanks.
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Opinions, worth about 2 cents

I have been using LifeSeal, a Boatlife product, for many years. There are other equally good choices. Like other sailors I would advice against 5200, or as Mr. Collins ("Maine Sail") calls it: the Devil's glue!
BTW, do not shy away from epoxy. If you use the West System stuff and follow the great printed guides from them it's pretty easy.

You might want to search out this subject on this site, and read narratives going back over a decade. Lots of helpful information.
 
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markvone

Sustaining Member
I used Sikaflex 291 for a thru hull replacement. Sikaflex 291 because that's what MaineSail generally uses and I didn't have a favorite. My old thru hull must have had a sealant because it popped right out after I took off the nut and bonked it with a hammer.

I would use any SEALANT you are comfortable with and avoid any of the ADHESIVES. You just need the sealant to make the job waterproof. You don't need an adhesive to hold the thru hull in the boat, it has threads and a nut. Some people think that if a fitting is held in mechanically that's good and adding adhesive is better. The fitting is designed to work mechanically and there are loads of threads here on this site revealing that almost every job will need to be taken apart sometime in the future.

Mark
 

JPS27

Member III
one last question on through hull sealant

The distinction between sealants and adhesives for this application is very helpful to relative newbies like me. I had definitely reviewed pages and pages of discussion on the topic on this board and others and found one thing consistent. There many opinions and many are contradictory. There are true believers for just about any type of adhesive or sealant. I see the strong argument for sealant given that the connection is mechanical. Thanks for that reminder. I definitely see the importance of being able to remove or replace components of this important system sometime in the future. The mainsail site mentioned that almost nothing on a boat is permanent and thus his choice of sikaflex 291.

One last question is did you use Lifeseal or Sikaflex 291 on all the connections? Especially the backing block to hull connection? I just want to be certain that if I choose to go with a sealant at the block-hull connection taht I'm not putting my boat and safety at risk. Thanks
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Sealants and Permanency

The distinction between sealants and adhesives for this application is very helpful to relative newbies like me. I had definitely reviewed pages and pages of discussion on the topic on this board and others and found one thing consistent. There many opinions and many are contradictory. There are true believers for just about any type of adhesive or sealant. I see the strong argument for sealant given that the connection is mechanical. Thanks for that reminder. I definitely see the importance of being able to remove or replace components of this important system sometime in the future. The mainsail site mentioned that almost nothing on a boat is permanent and thus his choice of sikaflex 291.

One last question is did you use Lifeseal or Sikaflex 291 on all the connections? Especially the backing block to hull connection? I just want to be certain that if I choose to go with a sealant at the block-hull connection taht I'm not putting my boat and safety at risk. Thanks

I would use either sealant, based on regular good reports. One other note about backing plates -- when we changed over to the "newer sale" Forespar sea cocks, they and their bases were bedded in epoxy. The idea was/is that the valve bodies are rebuildable from inside anyway. Also that way the stock mushroom head could be tightened on and when the epoxy kicked off the outside protruding part was ground off flush with the hull. Looks fine and fast and they are all working fine after over 15 years or so.
The yard might have used G10 for backing plates, but I honestly do not recall. It's been a long time.

I had to have one valve part replaced at a haul out and the base remains in place. As far as strength, this way the glass-reinforced valve body, and the GRP hull of the boat are all "one". (Kind of a high tech Zen thing.)
See reply #4 in this thread: http://www.ericsonyachts.org/infoex...vs-gate-valves-anyone&referrerid=28&styleid=8

They still look the same and work fine.

Loren
 
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markvone

Sustaining Member
For my thru hull replacement, I used Kitty Hair long strand Polyester filler between the backing block and the hull. I needed to have the backing block conform to a slight hull curve and an uneven surface.

https://www.amazon.com/Evercoat-868-Kitty-Reinforced-Filler/dp/B000Q8ICHY

You could also mix up some West System epoxy and thicken it with West 404 adhesive filler. The backer gets bonded to the hull. Sealant around the thru hull and it's threads.

My replacement was for a standard Marelon thru hull with a Marelon ball valve screwed on (for the engine seawater intake) - not an actual Marelon seacock or the new Marelon all-in-one valve that Loren references. It's worth investigating using one of these if you want to get rid of the Ericson factory thru hull and ball valve set up for all the reasons MaineSail states.

Using 1/4 inch thick G10 for backers is nice but difficult to cut. I use a wet tile saw which cuts easily but requires square backers. Cutting the round center hole with a hole saw is hard and the G10 eats hole saw bits. Dry fit everything to make sure you have enough thru hull threads exposed past the backer to add the thru hull nut and thread on whatever valve you are using. If you use 3/8 or 1/2 inch thick backers (of any material) with small size (5/8 or 3/4 inch) full thread Marelon thru hulls you will not have enough exposed threads.

Mark
 

bigd14

Contributing Partner
Blogs Author
G10

G10 cuts easily with a jig saw and an abrasive diamond blade. I trashed several table saw blades and created lots of foul smelling dust with a grinder before learning this!

And I use 291 for thru hulls and other sealing needs. Cleans up nicely with a Costco baby wipe followed by a little acetone.
 
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ChrisS

Member III
I just replaced three

I just repalced three thru hull and and seacocks on my 32-2, both 1.25" cockpit drains and the engine intake, which was .5" and I upsized to .75".

The setup was original thru hulls to 90 degree street els to ball valves. The original wood backing plates were damp, and some of the bronze fittings looked reddish and calcified. I thought after 43 years (at least for the thru hulls) I'd take this on.

Conflicting views abound: seacock vs. ball valves, 5200 or something less tenacious, wood backing blocks or G10. etc.

Basically I used Mail Sail's tutorial as a guide. I bought the Groco flange adapters. Note that Groco also makes a predrilled backing block, and there is also this guy on eBay that sells a verson with matching Groco bolt pattern, which I went with. Buying three backing blocks for $95 saved me some time.

FYI West Marine will also now price match Jamestown and Defender which came in handy.

Hauled in the yard I dissassembled the old fittings. Some were fused together, while others were barely connected!

One very surprising discovery was that the backing blocks were set deep into the hull. Once I chipped them out I was left with very uneven surfaces for the new backing blocks, and I was faced with a choice: sand the area flat, or build it up! I decided to mix up epoxy thickened with chopped fiberglass and colloidal silica. I then waxed the thru hulls and bolted them down, using them to sandwich the thickened epoxy between the backing block and the hull. After it cured, our came the thru hulls and the new backing blocks were bonded to the hull.

Should you choose to do this, make sure you thoroughly clean up/rough up the surfaces, and don't be stingy when you mix up the thickened epoxy; you want ample material to be between the backing block and the hull. Had I wanted to use 5200 and not thickened expoxy I think I would have had to sand the hull flat, and I didn't want to make the hull thinner.

I then make bronze studs from 5/16" bolts, and dry fit the entiire operation.

Once I was ready to install I used Sikaflex 291, mainly becuase not having make this repair before I wanted to make sure I would have been able to get the fittings apart; now that they are in and do not leak, I wish I would have used 5200 AS I NEVER HOPE TO TOUCH THIS AGAIN.
 

JPS27

Member III
These are helpful pics and explanation. Thanks. it spurred a few more questions.

I'm concerned about thickening the epoxy correctly. I've done plenty of epoxy work but none so critical. When referring to adding chopped fiberglass to the epoxy is that any old fiberglass fabric that one cuts up themselves or is that something off the shelf?

Related, I had assumed this kitty hair stuff was filler like the west systems' products. But it appears to have its own catalyst. The mainesail approach seemed to combine that with epoxy. Or am I misunderstanding his explanation?

I've been eyeing those groco plates and the knock offs. Glad to hear the knock offs work and that guy suggests that his material bonds to epoxy where the groco's not so much. How do you keep the epoxy from squishing up the open bolt holes? Seems like a mess waiting to happen.

Did you secure the plate with the thru hull while epoxy was curing simply with the T-H lock nut? I could imagine if using the flange you might get the epoxy bonding to the flange bottom.

My raw line is 1/2" as well. Is it ok to add a reducer from 3/4 to 1/2" to fit the water pump, or how best to do that? The only 1/2" seacock is a forespar model with NPS threads on both ends.

Thanks.
 
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Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
The hair of the (cat) that bit you...

https://www.westsystem.com/the-105-system/fillers/
While there are many choices, I have found that they are kind of similar for lower-tech jobs on our boat. I generally use the '404' thickener.
As for shaving your poor cat... :0 Leave him be.
"Kitty Hair" is a poly-resin product. I would not use it for boat projects just to avoid mixing the two types of resin technologies. Stick to epoxy.
While most anything will work in a pinch, a good grade of epoxy provides a superior bond, and the longer working time is a real help for us beginners.

Having mentioned the wonders of West Systems and their well-matched (and researched) additives, I must admit to using micro-balloons from Tap Plastic sometimes just because their store was closer to my house and cheaper.

Remember, mistakes can be rectified with a grinder and some 60 grit paper. :nerd:
And, of course, acetone and disposable vinyl gloves.
 

p.gazibara

Member III
We installed two thru-hulls before we left the PNW. We hauled out in pretty of Everett for an overnight hang in their slings and installed one forward for our head and a second aft for our sink.

On advice from the folks at Fisheries Supply I bought BoatLyfe white. We gooped it on, let it dry for a couple hrs then splashed. It was wild watching water come in from the two holes we put in our boat...

Back out we came and I called a friend who works at a yard terrified. He said try sikaflex or 4200, and put on way more than you think you need.

I tried again with 4200.

It worked like a charm, no leaks and the thru-hulls are great. The stuff apparently cures under water too.

I'm not sure if boatlyfe failed because we didn't put enough on, or we did something else wrong, but next time I'll again use 4200.

-P
 

markvone

Sustaining Member
Epoxy - Thicken it with West 404 adhesive filler. No need to add chopped fiber strands. You will use the 404 for plenty of other jobs. Epoxy is stronger but polyester is strong enough. Another advantage of epoxy, every time I've used Kitty Hair it's kicked super fast, like 2 minutes. No time for re-dos.

Kitty Hair is a thickened Polyester resin (thickened with fiber strands) that you add catalyst to harden. No sense getting it if you already have epoxy, just get the 404 filler.

I can't speak from experience for traditional seacocks. But you are bonding the backer to the hull using the thru hull and seacock parts as a clamp while the epoxy sets. Wax everything you don't want bonded and de-wax before you re-assemble with sealant.

Yes, a reducer is fine. I have a 3/4' engine intake thru hull and valve and use a 3/4 to 5/8 hose reducer to feed my raw water pump.

Mark
 
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ChrisS

Member III
In terms of fiberglass, I just cut up some cloth into 1/4" pieces. I also added colloidal silica to get the consistency right. When I set the backing block into the hull I already had the bronze studs in three of the holes; only a bit came up through the other three.

Yes, I used the thru hull nut, not the flange during the epoxy process.

Lastly I did add a reducer between a new Groco 3/4" strainer and the engine. BTW, Go to Marine has a nice compact bronze stainer for about $130 delivered. The engine runs about 5 degrees cooler with the larger thru hull. The original 1/2" had a screen on the outside, and also I had to modify the hull side to accept the new thru hull profile.
 

JPS27

Member III
bonding backing blocks to hull--how clean is clean

I'm moving slowly but getting there. I have almost all the parts for 4 through hulls. But I have backing blocks and silicon bronze bolts, washers, nuts. So I'm going to put the blocks down soon. But I'm finding it difficult to sand off the grey paint within the circumference of the blocks. Must I make sure I get all the paint off. Or is it good enough to make sure there is no loose paint? Will epoxy bond to that? Seems like I'd need to use paint stripper otherwise I'll being grinding into the hull and probably just grinding paint into the hull. Thanks for any advice.

IMG_0548.jpgIMG_0547.jpg
 

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
Can you reach the area with a palm sander? If so, put a sheet of 40 or 60 grit on it and rough up the surface. Clean it with some acetone on a rag. It's not good to try to bond to any paint.

I have also used a Stanley "Surform" hand tool to reach into tight spaces.
 
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JPS27

Member III
I tried my detail sander with 60 grit. it did not have the umphh needed. I think I'll try next my handy 1" paint scraper. The paint is tenacious, of course. And with that woven mat texture a good deal of the paint is down in crevices. I was trying not to eliminate too much fiberglass to get to the paint down in the valleys. After the scraper I'll try my orbital sander.
 

celtic sea

Member III
Hi, just my experience and opinion after 40+ yrs of my total 5 sailboats ..thru hulls on the exterior- 5200 no question. West system every where else. Although I used 5200 under backing plates on interior too. I don't plan on ever redoing them, feel secure and really isn't that bad as people make it out to remove if needed.
John
E35-2
SV DIJAN
 

markvone

Sustaining Member
The reason you want to get all/most of the paint off is to ensure a good bond of your backing blocks to the hull. You don't really know how well your block will bond to paint on the hull OR how well the paint is bonded to the hull.

The pictures below show my recent brain fart in bonding a big G10 backer for a new main track location to brown paint added to the hull throughout the boat by some previous owner at some time in the past. This paint is generally peeling off to some degree in most places. I was so concentrated on getting access to the other side, above the headliner in the quarter berth that I totally spaced on grinding the paint off of the easy side in the cockpit storage. I bonded the piece in on April 20 and just yesterday when I was in the storage area working on something else, the piece fell off on my head! You can see my white 404 thickened West epoxy could have been thicker and closer to the edge for a complete bond and it still bonded great to the paint, BUT the paint was not bonded well to the hull. The backer pulled the paint right off the fiberglass underside of the cockpit seat. Luckily, I can grind the cured epoxy off the G10 backer and do it over after sanding the rest of the brown paint off in the bond area.

Mark
 

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markvone

Sustaining Member
Sanding Fiberglass Tools

Hi Jay,

I usually start with 60 grit on my palm sander which works pretty well on my not-so-bonded brown paint. I use my Harbor Freight oscillating tool with a little 24 grit sanding triangle for really tight spaces but the paper wears out fast. I'd go to my 5 inch random orbital next and then my 7 inch sander/grinder if I have the space. A 2 or 3 inch 24 grit Roll Lock disc in a drill is like a little version of the 7 inch sander and a cheap way to get some serious sanding in a small space. I'll try this order to get the rest of the paint off the bottom of the cockpit seat.

https://www.amazon.com/WD-Tools-106...6008&sr=8-14&keywords=roll+lock+discs+24+grit

To clean the cured epoxy off my de-bonded G10 backer for round two, I went right to the 7 inch sander with 60 grit. I had the backer out in the driveway and it took all of 5 minutes to grind off the paint and epoxy.

Mark
 

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