Marine sealant Vs. Silicone

So in another thread someone said silicone is not marine sealant and I should not be using it.

so I went and bought a tube of Marine Sealant. and I hate to say it but this stuff is Terrible.

It does not stick to anything. I am filling some hole from moving tab on my transom. I cleaned the old holes out, put some marine sealant on it. and the selant would not stay on the hole. it only stuck to the end of the tube. I had to push it into the hole with my finger. and then most of it stuck to my finger not the transom.

I stuck the bolt in and the stuff rolled up around the bolt into a ball, still barely sticking to the transom. I tried to spread it out and make a fillet around the screw... what a nightmare.

Silicone has always worked well for me. a little dab, put the screw in, smooth with a finger.. done.

YEs I cleaned the transom before I tried to stick it to it.

So my question is Why this junk, why NOT 100% pure clear silicone? or was the guy telling me NEVER to use silicone full of it??

Thanks a bunch

Re: Marine sealant Vs. Silicone

chances are you got an old batch...take it back.......there is NO WAY you could roll a ball of 5200 up....the stuff is so sticky.... use coveralls and gloves when i use it

Re: Marine sealant Vs. Silicone

Oh it sticks to my fingers...

anyways that still does not answer Why I should NOT use silicone?

Re: Marine sealant Vs. Silicone

I believe the thinking is that using silicone (not caulking as it is different) below the waterline is a recipe for disaster because it can fail over time in the typical conditions a normal boat sees, and a failure of the sealant can be big trouble.

Caulking IMHO has little place on a boat, and above the water line real silicone is fine.

Not sure if you keep you boat in the water or trailer etc, but be sure to seal up those holes good and permanent so you do not get any water penetration into your transom no matter what product you use.

If your not using the holes again consider using epoxy.

One last thought is that I am pretty sure if you try to apply 3M 5200 to wet wood it does not stick nearly as well as it does to your hands and clothes.

Re: Marine sealant Vs. Silicone

Silicone is easy to remove and can fail in a short amount of time. I've used it before, before I knew any better, and it didn't last too long. If you have ever removed silicone and marine sealant, you will know the difference in the bonding power. Some marine sealants can remove paint and gelcoat,,, while trying to break their bond.

I agree with oops that you probably got a bad batch. I just used some tonight and it was sticking to anything and everything it touched. There are different consistencies and the old slow cure 5200 is kind of runny and will drip and run easily. I used some Attwood 7200 fast cure and it was a lot thicker and wouldn't run, which I was expecting it too (hoping it would).

What size of holes were you trying to fill and what type of sealant were you using (3m 5200, 4200, fast cure/slow cure, Attwood, Boatlife, etc, etc..) ?

Oh yeah, out here in the desert you need to "kick" the sealant with moisture. Drape a moist towel over the area and then a garbage bag to hold in the moisture. Don't let the towel touch or water drip onto the sealant or it will mess up your nice fillet. If it's a small part, stick it in a bucket with some water, suspending the part above the water.

Re: Marine sealant Vs. Silicone

Thanks Lenny,

I had just washed the transom off, because there was an oliey film on it. I figured a clean non oily surface would be best.

The boat sits on a trail most of the time. Some holes I was sealing up permanently. epoxy is a good idea for those. I actually bought some "screws" that fit the hole. tried to put the marine stuff in the hole. the stuff the bolt in the hole. I mean it did work, but I was not impressed wit hthe marine stuff.


My question was really about why NOT to use silicone. Yes I agree caulking NO WAY.. I used the 100% silicone stuff. plain old clear silicone adhesive sealant that comes in a caulking type tube.

thanks for the input

Re: Marine sealant Vs. Silicone

Silocone does not adhere to fiberglass very well. The 5200 is an adhesive/sealant so it adheres very well to everything including your fingers. You can also use what is called lifeseal below the water line. Lifeseal is more of the consistancy of silocone and is much easier to use than the 5200. I always use 5200 below the water line. In the future if you have something above the water line, try the silocone 1 hour or two hour dry time stuff. It does adhere very well. I have used it around my fuel tank hatch and it looks as good as it did two years ago when I installed it. Stick with the 5200 for under water.

Once done using the 5200, the only way I have found to save the rest of the 5200 for further use is the vacumm seal it. Krgers has those cheap ziplocks that come with a manual pump, they work well, then I put it in the freezer.

By the way, simple explaination on the silocone, have you ever used it in a shower? Doesn't last long even in a shower where its not under water most of the time. But like I said, above water line, 1 or 2 hour dry time stuff works great.

Re: Marine sealant Vs. Silicone

If you have 4200 or 5200 and it wont stick, then theres an issue sumwhere.....that stuff sticks on everything, but its the best. It will surely seal it up when dry, skims over in about 30 mins.

Re: Marine sealant Vs. Silicone

You can test this theory...... on the bottom of your transom clean and lightly sand...... place a 2" line of silicone and a 2" line of 3m5200 and at the end of a season ......peal them off. The silicone will peal away w/o problem (if it is still there) and the 3m will be there.

I have found silicone fails too early and too soon. It lacks the real bite needed in a marine use. I have swapped out many motors for people who used silicone around the bolts and there transoms were wet. I was able to just peal it away.

Now there are various marine grade caulk.

3m 5200 is PERMANENT
3m 4000 is removable but not too easy

There are others on the market however, 3m 5200 is available at home depot in the glue area in smaller tubes. Once you open a marine sealant you are almost always committed to using it since it will more than likely cure in the tube.

Re: Marine sealant Vs. Silicone

In the long run it will not matter which product you use. Transom + sealant = rotten transom
Sealants, including 5200 and 4200, are responsible for more transom replacements than all other causes combined.

Re: Marine sealant Vs. Silicone

New to boating, not so new to epoxies, sealants, etc. Let me see if I understand this properly.

• Epoxy for permanent repairs.
• 3M 5200 for below the waterline repairs that may need to be redone.
• Silicone and other house/automotive sealants for above the waterline.

Are stingers inside the boat considered "above" the waterline? The old owner fastened something into them (not through holes) and I want to repair them correctly. I was told to use fiberglass resin, but you have to mix it as well. FWIW, the boat is fiberglass.

Re: Marine sealant Vs. Silicone

thanks for the input guys.


digbat. your comment has me confused. if no water can get to the transom hows it gonna rot? my transom is 40+ yeas old. and it's solid as a rock. it has quite a few "holes" in it that have scews in them looks like there was a ladder on it at one point, a fish finder. and who knows what else. I filled all those holes with silicone, then pit screws in them to make sure they stay.


3m sealant was not available here. I used "goop" brand Marine sealant it came in a "calking gun" tube.

http://www.biosafe-inc.com/marine.htm



someone said have you used silicone in the shower?? no NEVER. but I have used caulking in the shower.. way different.

I have used PURE silicone to seal several fish tanks. my 200 gal tank was resealed 8 years ago. and the silicone is just as solid today as it was then. it has discolored and turned greenish but it has not peeled or leaked. and it's been underwater 24 hrs a day 365 days a year.

Again thanks for the input. I am going to check out the results this morning. I might be a little happier today than I was last night. although making the "fillets" looks smooth was a pain. if it sealed properly, I am good to go.

Re: Marine sealant Vs. Silicone

metalwizard said:

thanks for the input guys.


digbat. your comment has me confused. if no water can get to the transom hows it gonna rot? my transom is 40+ yeas old. and it's solid as a rock. it has quite a few "holes" in it that have scews in them looks like there was a ladder on it at one point, a fish finder. and who knows what else. I filled all those holes with silicone, then pit screws in them to make sure they stay.


I have used PURE silicone to seal several fish tanks. my 200 gal tank was resealed 8 years ago. and the silicone is just as solid today as it was then. it has discolored and turned greenish but it has not peeled or leaked. and it's been underwater 24 hrs a day 365 days a year.

Click to expand...

There are 4 major factors that determine the weathering of a sealant.
1: temperature
2: humidity
3: ultra-violet radiation
4: mechanical loading

A critical attribute of an effective sealant is the ability to span and seal gaps between dissimilar materials. These materials experience daily (~?7%) and yearly cycles (~?25%) of strain deformation. As these materials are exposed to the weather, molecular changes occur that eventually prevent the sealant from responding to these imposed strains, leading to failure of the sealant.

A boat isn't an aquarium. Given the contributing factors above, there is no way you can not relate the performance of a sealant in an aquarium to a boat by any stretch of the imagination. May I suggest some reading on the proper repair of holes in a transom
http://www.westsystem.com/ss/assets/HowTo-Publications/Fiberglass-Boat-Repair-and-Maintenance.pdf

Re: Marine sealant Vs. Silicone

Great answer, that is a GOOD "WHY" although I don't see much loading in the application I am using it for

(I am sealing a bolt into a small hole to plug the hole up.)

I could see NOT using it for a lot of other things.

Re: Marine sealant Vs. Silicone

metalwizard said:

thanks for the input guys.


digbat. your comment has me confused. if no water can get to the transom hows it gonna rot? my transom is 40+ yeas old. and it's solid as a rock. it has quite a few "holes" in it that have scews in them looks like there was a ladder on it at one point, a fish finder. and who knows what else. I filled all those holes with silicone, then pit screws in them to make sure they stay.


3m sealant was not available here. I used "goop" brand Marine sealant it came in a "calking gun" tube.



http://www.biosafe-inc.com/marine.htm

someone said have you used silicone in the shower?? no NEVER. but I have used caulking in the shower.. way different.

I have used PURE silicone to seal several fish tanks. my 200 gal tank was resealed 8 years ago. and the silicone is just as solid today as it was then. it has discolored and turned greenish but it has not peeled or leaked. and it's been underwater 24 hrs a day 365 days a year.

Again thanks for the input. I am going to check out the results this morning. I might be a little happier today than I was last night. although making the "fillets" looks smooth was a pain. if it sealed properly, I am good to go.

Click to expand...

If you had used the 3M 5200 you wouldn't be writing this. An alternative is Marine Tex which is a two part epoxy and will cure under water and hardens like steel.

Re: Marine sealant Vs. Silicone

metalwizard said:

So in another thread someone said silicone is not marine sealant and I should not be using it.

so I went and bought a tube of Marine Sealant. and I hate to say it but this stuff is Terrible.

It does not stick to anything. I am filling some hole from moving tab on my transom. I cleaned the old holes out, put some marine sealant on it. and the selant would not stay on the hole. it only stuck to the end of the tube. I had to push it into the hole with my finger. and then most of it stuck to my finger not the transom.

I stuck the bolt in and the stuff rolled up around the bolt into a ball, still barely sticking to the transom. I tried to spread it out and make a fillet around the screw... what a nightmare.

Silicone has always worked well for me. a little dab, put the screw in, smooth with a finger.. done.

YEs I cleaned the transom before I tried to stick it to it.

So my question is Why this junk, why NOT 100% pure clear silicone? or was the guy telling me NEVER to use silicone full of it??

Thanks a bunch

Click to expand...

metalwizard said:

Oh it sticks to my fingers...

anyways that still does not answer Why I should NOT use silicone?

Click to expand...

metalwizard said:

Thanks Lenny,

I had just washed the transom off, because there was an oliey film on it. I figured a clean non oily surface would be best.

The boat sits on a trail most of the time. Some holes I was sealing up permanently. epoxy is a good idea for those. I actually bought some "screws" that fit the hole. tried to put the marine stuff in the hole. the stuff the bolt in the hole. I mean it did work, but I was not impressed wit hthe marine stuff.


My question was really about why NOT to use silicone. Yes I agree caulking NO WAY.. I used the 100% silicone stuff. plain old clear silicone adhesive sealant that comes in a caulking type tube.

thanks for the input

Click to expand...

metalwizard said:

thanks for the input guys.


digbat. your comment has me confused. if no water can get to the transom hows it gonna rot? my transom is 40+ yeas old. and it's solid as a rock. it has quite a few "holes" in it that have scews in them looks like there was a ladder on it at one point, a fish finder. and who knows what else. I filled all those holes with silicone, then pit screws in them to make sure they stay.


3m sealant was not available here. I used "goop" brand Marine sealant it came in a "calking gun" tube.

http://www.biosafe-inc.com/marine.htm

someone said have you used silicone in the shower?? no NEVER. but I have used caulking in the shower.. way different.

I have used PURE silicone to seal several fish tanks. my 200 gal tank was resealed 8 years ago. and the silicone is just as solid today as it was then. it has discolored and turned greenish but it has not peeled or leaked. and it's been underwater 24 hrs a day 365 days a year.

Again thanks for the input. I am going to check out the results this morning. I might be a little happier today than I was last night. although making the "fillets" looks smooth was a pain. if it sealed properly, I am good to go.

Click to expand...

metalwizard said:

Great answer, that is a GOOD "WHY" although I don't see much loading in the application I am using it for

(I am sealing a bolt into a small hole to plug the hole up.)

I could see NOT using it for a lot of other things.

Click to expand...

So you used "Marine" grade "sealant" .. what brand ? ..

Silicone is for Above the waterline ONLY ! And for limited applications ..

Seems to me that you want an easy way to fill a small hole with something you have on hand .. or your trying to start an Silicone VS. 3m thingy ..

Im sure most of us will suggest the Right way to do things .. and if you argue the "well why" .. then its going to be mostly " because this is how its done correctly ".

Some here might be able to tell you the chemical and water thingys of said application with silicone ( or whatever you preferred method argument might be ) is bound to fail with chemical this and that .. I think your get the gist of what the members are saying.. its Just not a Good practice to put silicone Below the waterline in Any way.

Take it or leave it .. its up to you and your boat.

Peace..

YD.

Re: Marine sealant Vs. Silicone

If the hole was wet, the 5200 won't stick, it just balls up. That was my experience, anyway. Make sure the hole is dry. I love 5200, just wish it would cure in 2 hours. LOL
I keep my tube of unused in a baggie in the freezer. Clean the top 3/8 inch out and your good to go.

Re: Marine sealant Vs. Silicone

Yacht Dr. said:

So you used "Marine" grade "sealant" .. what brand ? ..

Silicone is for Above the waterline ONLY ! And for limited applications ..

Seems to me that you want an easy way to fill a small hole with something you have on hand .. or your trying to start an Silicone VS. 3m thingy ..

Im sure most of us will suggest the Right way to do things .. and if you argue the "well why" .. then its going to be mostly " because this is how its done correctly ".

Some here might be able to tell you the chemical and water thingys of said application with silicone ( or whatever you preferred method argument might be ) is bound to fail with chemical this and that .. I think your get the gist of what the members are saying.. its Just not a Good practice to put silicone Below the waterline in Any way.

Take it or leave it .. its up to you and your boat.

Peace..

YD.

Click to expand...

I really was not trying to start a war or say one BRAND is better than the other. I have used silicone (the real silicone) for lots of waterproofing type jobs. with great luck. so I was really curious why NOT to use silicone and why to use "marine" sealant. (which i never really had heard of) I was always under the impression that TRUE silicone was the best sealant for water.. period. I now know I did not have all the proper info... and my assumption was incorrect. and I was truly surprised

I got lots of great input. now I basically know Why I should NOT use silicone. so I got the answer I wanted. even though it really was NOT what I was expecting. so bottom line this thread did exactly what I hoped for.. it answered my question, it enlightened me on something I had never heard of. and it steered me in the right direction.. so I learned something new. and I may have saved myself some problems in the Future..

that was until I read your post. it was the longest overdone post to tell me "well thats just the way you do it"

That quote tells me one thing you have NO idea why you do it that way. you just do it because someone told you thats the way you do it. to me that is VERY uneducated... to follow someone jsut because they say so is pretty dumb... if I went and played on the freeway and told you to do it because I said you should.. who would be the most foolish.. me for telling you to? or you for doing without any background or thought..... think about that a bit.


Thanks to everyone for their enlightening input.. my question was answered extremely well. thats why I come to this forum... with a few stupid exceptions there is an AWESOME accumulation of Experience and mental power here unlike anywhere else..


now I am going to grab my ball and go down to the hwy and shoot some hoops.. wanna come with me??

Re: Marine sealant Vs. Silicone

metalwizard said:

now I am going to grab my ball and go down to the hwy and shoot some hoops.. wanna come with me??

Click to expand...

Hmmmmmm haven't shot hoops in some time (real bad knees) but, with some practice I could

Re: Marine sealant Vs. Silicone

I'd use marine tex in those holes!