# Is Marine Silicone any different?



## tausap

I was looking at clear non-adhesive silicone sealant today. The "Marine grade" stuff is much more expensive than the "bathroom" grade at Home Depot. Is there a significant enough difference to pay the extra, or is it just a marketing gimmick?


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## sailingdog

What are you using it for. Silicone-based sealants have very little good use on a boat, other than bedding lexan/acrylic glazing, covering the ends of cotter pins and being used on the bottom of dishware to make it non-skid.

Using it on deck hardware is really a bad idea, since all silicone sealants tend to leave behind contaminants that make resealing the area afterwards almost impossible.


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## AllThumbs

To answer your question, I don't know, but somehow I doubt they are different. I guess that is not helpful...


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## bobmcgov

Two major kinds of silicone sealants: those with acetic acid (vinegar), and those without. You want the kind without, as the acetic acid can really pit and corrode marine fittings. If you are sure this is a job for silicone (as SD says, it's right for very few boat jobs), use GE Silicone II Sealant, available at your local hardware store. Still about $6 a tube. GE Silicone I is acetic-based, so don't use that.


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## nightowle

learning these seemingly small facts is what makes this forum great. I just love picking up these tips! Now I just have think where I may have used the vinegar smelling silicone around the boat!!!! oops!


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## sailingdog

The problem with the acetic acid-based silicone is that it tends to attack metals... because of the acid. Fortunately, acetic acid isn't all that aggressive an acid.


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## scottyt

i have a tube of this stuff on board as my general sealing/adhesive stuff ( also have 4200 ). it a liquid nails product, that is very clear when cured. it sets up pretty quick and is not hard to remove later. if i had to give it a 3m comparison i would say its a little weaker than 4200 but has better flexibility. i used it to seal the plex on my roof hatch, and you have to look to see it. i see it as my 4200 replacement when i dont want the white or want it clear.


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## jarcher

*What about the hybreds?*

This seems like a good thread to ask this... What about those sealants that are half silicon and half something else? It would seem that they have the same issue as silicon (contaminating fiberglass) but many people use lifecaulk and other hybreds.


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## jason3317

Spinlock specifically points out in their documentation that polysulphides and urethanes should NOT be used to bed their rope clutches; they want silicone to be used. Reasoning provided is that the polys will degrade the plastic materials? So, I will hope that I never have to rebed. 

How do you clean the contaminant residue left behind to get a good seal when rebedding?


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## Maine Sail

*Silicone*



jason3317 said:


> How do you clean the contaminant residue left behind to get a good seal when rebedding?


You will need to sand it after removing as much as you can by hand. Tape off the areas you don't want sanded and then sand the contaminated area. Certain plastics can have the plasticizers leeched out of them over time from products like polysulfides. This leeching makes the brittle and more prone to failure. In these situations I would recommend Dow 795 as the Silicone of choice..

As Dog stated silicone has very, very few good uses on a boat. Certain plastics require it because they can be attacked by Polysulfides, Polyurethanes or Polyethers.

The problem with Silicone is that it nearly permanently contaminates a surface. Even when you think it is gone and you've rubbed it away it is still there. Simply use a spray bottle, like for ironing, and mist the surface it the water beads the surface is contaminated.

Silicone was and is designed to resist attack by most all chemicals. None of the commercially, body shop strength, removers are really all that safe for fiberglass and even they don't work all that well even on metal.

Once you've used silicone it will be very tough to get anything else will stick to where you had the silicone.

There are also MANY grades of silicone and it goes much deeper than just marine or bath tub. Acrylic hatches should only ever be sealed with Dow 795 or GE SG4000 as these are "structural grade" Silicone products. Bath tub silicone is not even rated as such and should not be used to seal ports or hatches as it is just not safe or prudent behavior.

If you are going to choose a Boat Life product stay away from the combo Life Seal product as you WILL get silicone contamination and choose Life Calk for general bedding uses unless certain plastics like Polycarbonate or Acrylic..

For those of us who have had to atually remove silicone contamination, for paint work, I can asure you the ONLY way to 100% get rid of Silicone contamination of gelcoat is to sand it off.. Just because you can't see it does not mean it is not there, trust me!!


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## sailingdog

You could always use butyl tape instead. It won't attack plastics to my knowledge and is a very good sealant.


jason3317 said:


> Spinlock specifically points out in their documentation that polysulphides and urethanes should NOT be used to bed their rope clutches; they want silicone to be used. Reasoning provided is that the polys will degrade the plastic materials? So, I will hope that I never have to rebed.
> 
> How do you clean the contaminant residue left behind to get a good seal when rebedding?


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## LarryandSusanMacDonald

*Maine Sail said:*



> The problem with Silicone is that it nearly permanently contaminates a surface. Even when you think it is gone and you've rubbed it away it is still there. Simply use a spray bottle, like for ironing, and mist the surface it the water beads the surface is contaminated.
> 
> Silicone was and is designed to resist attack by most all chemicals. None of the commercially, body shop strength, removers are really all that safe for fiberglass and even they don't work all that well even on metal.
> 
> Once you've used silicone it will be very tough to get anything else will stick to where you had the silicone.


A friend of mine, who spray paints boats for a living absolutely HATES silicon. He says, "The only place silicon belongs on a boat is in the top half of a bikini. And you don't even need the bikini."


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## sailingdog

That's wrong in so many ways, but so appropriate... 


LarryandSusanMacDonald said:


> *...*He says, *"The only place silicone belongs on a boat is in the top half of a bikini. And you don't even need the bikini.*"


BTW, it is Silicone, not Silicon, one is used as a sealant, the other in solar panels and micro-chips.


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## LarryandSusanMacDonald

> BTW, it is Silicone, not Silicon,


You're right - my bad. I think they use it to make sand, too.


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## kreed17er

This thread has really helped me. I am in the process of removing the hardware from my Macgregor Venture 17 and have found a ton of silicone. Looks like the installer went nuts with the stuff. I will try what you guys suggested and let you know how it goes.


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## AllThumbs

Back to the OP original question, I have used the bathroom variety silicone in an environment that is much harsher than a marine environment. Namely in my bathroom. Around the tub to be specific. It's wet almost all the time (3 teenagers), gets subject to harsh chemicals weekly and has lasted 10 years, and still looks fine.

I am 99% certain that marking the stuff "marine grade" is a marketing ploy designed to fool us into paying 3X the price for the same product.

I am not saying it's appropriate for any particular application, I am saying it's prolly not any better than the hardware store stuff.

Eric


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## jason3317

Maine Sail said:


> I would recommend Dow 795 as the Silicone of choice..


Where can this product be sourced?



Maine Sail said:


> Once you've used silicone it will be very tough to get anything else will stick to where you had the silicone.


Will a reapplication of silicone have the same problem sticking, or is it just other sealants on top of old silicone the problem?


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## AllThumbs

jason3317 said:


> Where can this product be sourced?
> 
> Will a reapplication of silicone have the same problem sticking, or is it just other sealants on top of old silicone the problem?


It's mostly paint that will never stick AFAIK. What is the application?

The PO of my boat used silicone to bed the hardware. Since then I have removed all the silicone (with a knife, then sanded whatever residue that was left) and repainted and rebedded with 3M 101 Polysulfide. Time will tell how well the paint sticks and the 3M 101 works.

I will say that the silicone bedded hardware did not leak.


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## sailingdog

*Amazon.com *has it. A simple google search would have found it for you.


jason3317 said:


> Where can this product be sourced?


Pretty much everything has problems sticking to where the silicone was, even new silicone. 


> Will a reapplication of silicone have the same problem sticking, or is it just other sealants on top of old silicone the problem?


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## knothead

Hey, you guys gave me an idea. 

Since 5200 sticks too well, and since silicone leave a residue that prevents other products from sticking well. The solution is simple.

*Apply silicone and then remove it from anyplace you want to use 5200*. 

Boy, I'm a genius. :laugher


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## jason3317

sailingdog said:


> *Amazon.com *has it. A simple google search would have found it for you.QUOTE]
> 
> Yes, I found it online. But, I really meant locally....just didn't clarify perfectly...my bad.


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## sailingdog

LOL... if you call Dow, I'm sure they have a list of vendors that they can give you that would stock it locally. 


jason3317 said:


> Yes, I found it online. But, I really meant locally....just didn't clarify perfectly...my bad.


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## tausap

Wow, I never thought I would get this much out of the thread, but I have learned a lot. Do you think Silicone is inappropriate for the final seal around the mast boots I am putting on?


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## sailingdog

See previous post above that says:



sailingdog said:


> What are you using it for. Silicone-based sealants have very little good use on a boat, other than bedding lexan/acrylic glazing, covering the ends of cotter pins and being used on the bottom of dishware to make it non-skid.
> 
> Using it on deck hardware is really a bad idea, since all silicone sealants tend to leave behind contaminants that make resealing the area afterwards almost impossible.


What do you think?? Is it a lexan or acrylic port? Is it a cotter pin?? Is it dishware for use in the galley??? No...

There's your answer.


tausap said:


> Wow, I never thought I would get this much out of the thread, but I have learned a lot. Do you think Silicone is inappropriate for the final seal around the mast boots I am putting on?


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## nmccubbin

We have had good results with Sikaflex. I like it better than 4200 or 5200


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## tausap

sailingdog said:


> See previous post above that says:
> 
> What do you think?? Is it a lexan or acrylic port? Is it a cotter pin?? Is it dishware for use in the galley??? No...
> 
> There's your answer.


A simple no would suffice.


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## TSOJOURNER

Help!!!

My non-opening lexan port leaks bad. I used Sikaflex and it still leaks.
Any recommendations like Lifechalk or Lifeseal?
I need to have the product in black.

Your input and is greatly appriciated


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## AllThumbs

Butyl tape?


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## jarcher

TStein said:


> Help!!!
> 
> My non-opening lexan port leaks bad. I used Sikaflex and it still leaks.
> Any recommendations like Lifechalk or Lifeseal?
> I need to have the product in black.
> 
> Your input and is greatly appriciated


How did you apply the sealant? I am in the process of fixing the same problem, but the only way to do it right is to disassemble the dead light, clean off all the old sealant, and rebed/reassemble.

If you just tried to seal it from the outside you will meet with limited success.


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## sailingdog

Which SikaFlex did you use??? Also, did you disassemble the port and re-bed it, which as Jarcher points out, is the only really correct way to fix a leaking port. Butyl tape is a good sealant for lexan ports and does come in black. Some sealants, like polysulfide-based ones will attack the lexan, others like some polyurethane sealants, will be damaged by the plasticizers used in the lexan.



TStein said:


> Help!!!
> 
> My non-opening lexan port leaks bad. I used Sikaflex and it still leaks.
> Any recommendations like Lifechalk or Lifeseal?
> I need to have the product in black.
> 
> Your input and is greatly appriciated





jarcher said:


> How did you apply the sealant? I am in the process of fixing the same problem, but the only way to do it right is to disassemble the dead light, clean off all the old sealant, and rebed/reassemble.
> 
> If you just tried to seal it from the outside you will meet with limited success.


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## anthon

I never knew there was so many different types of Silicone Sealant!


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## Nooga

What is used to provide a seal between the rub rail and boat?


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## August Moon II

Once it cures out the issue is gone.
If boat is ventilated the vapors will be removed.
Same acid as vinegar.


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## pdqaltair

Nooga said:


> What is used to provide a seal between the rub rail and boat?


A high to medium strength polyurethane like Sika 291.

Locktite PL S40 (also polyurethane, same strength and elasticity) is a very similar product for 1/3 the price (Home Depot). It is the only hardware store product I would use for this sort of application. I can only assume it is cheaper because they sell more. I've used it on the boat for years. Just one of a thousand money saving expedients that help keep boat maintenance affordable. See "Peanuts," below.

Loctite PL S40 10 fl. oz. White Polyurethane Window, Door and Siding Sealant-1675293 - The Home Depot

Also available in black (PL S30), which can be handy for repairing gaps in black rubrails.

---

In general, polyurethanes are very messy to work with. If you want a neat job, mask it first and pull the tape as soon as you have smoothed the sealant (before it begins to cure). Since humidity in the air is the curing agent for polyurethanes, high humidity is not a problem, but he surfaces must free of liquid water.


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## midwesterner

sailingdog said:


> LOL... if you call Dow, I'm sure they have a list of vendors that they can give you that would stock it locally.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> jason3317 said:
> 
> 
> 
> Yes, I found it online. But, I really meant locally....just didn't clarify perfectly...my bad.
Click to expand...

Some of the availability is regional and has to do with where boats tend to live. I searched online for 3M 5200 and, although Home Depot carries it and lists it on their website, they did not have it in any of the my local stores here in the Midwest.

Just out of curiosity, I called two stores on the east coast in Maryland and North Carolina and they had plenty of it in the store. I called a local boat dealer (we're talking just ski boats and bass fishing boats) and they said they could order some and have it in a week but their price was considerably higher than the online price through Home Depot.

I contacted 3M and they said that their product is carried through NAPA auto parts stores. My local NAPA Auto Parts store was able to get a tube within two days at a price that was comprable to the cheapest price I could find anywhere online and, with no shipping charges.


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## pdqaltair

midwesterner said:


> Some of the availability is regional and has to do with where boats tend to live. I searched online for 3M 5200 and, although Home Depot carries it and lists it on their website, they did not have it in any of the my local stores here in the Midwest.
> 
> Just out of curiosity, I called two stores on the east coast in Maryland and North Carolina and they had plenty of it in the store. I called a local boat dealer (we're talking just ski boats and bass fishing boats) and they said they could order some and have it in a week but their price was considerably higher than the online price through Home Depot.
> 
> I contacted 3M and they said that their product is carried through NAPA auto parts stores. My local NAPA Auto Parts store was able to get a tube within two days at a price that was comprable to the cheapest price I could find anywhere online and, with no shipping charges.


I'm telling you, try Locktite PL S40. Strongest overall, better than 3M5200 for most materials, for 1/3 the price. I've been using it for 15 years. And Home Depot stocks it.

Marine Sealant Adhesion Tests - Practical Sailor Print Edition Article

Sail Delmarva: More Shoe Repair

I even use it for shoe and boot repair. This pictures is several years after the repair, after many mountain miles (it is available in black or white). All around the toe and 4 inches down the inside is PL S30.


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## Barquito

pdqaltair said:


> I'm telling you, try Locktite PL S40. Strongest overall, better than 3M5200 for most materials, for 1/3 the price. I've been using it for 15 years. And Home Depot stocks it.
> 
> Marine Sealant Adhesion Tests - Practical Sailor Print Edition Article
> 
> Sail Delmarva: More Shoe Repair
> 
> I even use it for shoe and boot repair. This pictures is several years after the repair, after many mountain miles (it is available in black or white). All around the toe and 4 inches down the inside is PL S30.


That and a little duct tape...


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## Tanski

Boat shopping if I find silicone used to "seal" anything I walk away and look for another boat!


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## flyingriki

Aside from the good advice on where and were not to use silicone on a boat I found a wide variety of stickiness between different "100% silicones". Tried several kinds to stick pairs of rubber squares together and let them cure. Some stuck a little, some very little and a couple really well. Big differences.


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