Marine Sealant vs Epoxy

[Randy18540]

Am going to replace my transducers for depth and speed, which are both installed through the hull. Instructions vaguely call for marine sealant ( what and where to get appropriate stuff? ). Is epoxy just as suitable? Epoxy mixed with chopped cotton ( aka flox )? Silicon sealant? I have much to learn.
Thank You in advance.

 

[Hermit Scott]

You will want to use marine sealant for sure. Something for underwater. I used a product called sikiflex (I think 292 or 291)for my through hulls. Silicone is not suitable on boats IMHO. Epoxy is not used for sealing transducers, due to the difficulty of removing it later and if your transducers are plastic won't stick to them anyway.
Expect to spend $20 or so a tube at a West marine store. They are located everywhere, even in land locked San Antonio. You can get them cheaper online, BUT this stuff hardens up in the tube as it gets old. I am the king of all cheapskate bargin hunters, but for sealant I just go to the store and buy it so I know it's not already setting up.

 

[sailingdog]

I'd highly recommend you read the post I wrote on marine sealants... and use something like 3M 101. Be aware that 3m 101 has a fairly long cure time (two weeks or so) and should not be submersed for at least 24-48 hours after application, and needs to be applied when the temps are above 50˚ F IIRC.

 

[Maine Sail]

I'd highly recommend you read the post I wrote on marine sealants... and use something like 3M 101. Be aware that 3m 101 has a fairly long cure time (two weeks or so) and should not be submersed for at least 24-48 hours after application, and needs to be applied when the temps are above 50˚ F IIRC.

Just an FYI but 3M 101 was recently discontinued.:cussing: That leave only Life Calk as the sole polysulfide..

Two of my other favorites, for a lower adhesion product, are Sikaflex 201US and Sikaflex 295UV. Both are polyurethanes that are under 175 PSI adhesion and over 500% elongation before break..

 

[Ed Schenck]

Is the question about new thru-hulls or new transducers inside original thru-hulls? And does the answer change?. My new Nexus thru-hulls actually shipped with a small tube of silicone(back in the day).

 

[sailingdog]

Just an FYI but 3M 101 was recently discontinued.:cussing: That leave only Life Calk as the sole polysulfide..

Two of my other favorites, for a lower adhesion product, are Sikaflex 201US and Sikaflex 295UV. Both are polyurethanes that are under 175 PSI adhesion and over 500% elongation before break..

damn... i was afraid of that... in that case, I'd go with Sikaflex 295...

 

[higgs]

Whatever you decide DO NOT use something permanent like epoxy, 5200, etc. The day may well come when you want to undo the job. I have had good success with Life Seal - or is it Life Calk? I can never remember which one is for below the waterline, but the package will let you know.

 

[Blitz]

Life Seal / Life Calk

I have had good success with Life Seal - or is it Life Calk? I can never remember which one is for below the waterline, but the package will let you know.

Both, but Life Seal is more for through hulls

 

[Maine Sail]

Both, but Life Seal is more for through hulls

Personally I do not like using silicone or silicone hybrids, like Life Seal, for below waterline fittings even though Boat Life says it's OK. Life Seal is a combination of silicone and polyurethane.

The silicone can contaminate the hull so the next time you re-seal an underwater fitting it may never seal correctly. Most companies do not recommend silicone for below waterline use, 3M included. Boat Life feels comfortable with their PU/silicone combo but I would choose Life-Calk (polysulfide) over Life Seal every time for that application..

One reason I dislike Boat Life products is their confisng marketing. You need to be VERY careful buying LifeCalk and Life-Calk.

Just noticed this on the Boat Life web site. I hope it is a typo!!


LifeCalk is a 100% silicone based product.

Life-Calk is a 100% polysulfide sealant..

Bad marketing 101?

 

[Nik]

No more 3M 101... DAMNIT... Took forever to cure, but great stuff to use (In the proper application).

 

[Blitz]

One reason I dislike Boat Life products is their confisng marketing. You need to be VERY careful buying LifeCalk and Life-Calk.

Just noticed this on the Boat Life web site. I hope it is a typo!!


LifeCalk is a 100% silicone based product.

Life-Calk is a 100% polysulfide sealant..

Bad marketing 101?

Good Catch - that is confusing

 

[Maine Sail]

Good Catch - that is confusing

I called Life Industries today and made them aware of the wording on the site regarding silicone/polysulfide. It was in fact a mistake. They said they will make changes to the web site as soon as they can. I assumed it was wrong, but you never want to assume, so I called...

 

[Prime Time]

4200

I called Life Industries today and made them aware of the wording on the site regarding silicone/polysulfide. It was in fact a mistake. They said they will make changes to the web site as soon as they can. I assumed it was wrong, but you never want to assume, so I called...

I have used 3M 4200 with excellent results for thru hulls. Doesn't have the nasty adhesion of 5200.

 

[Maine Sail]

I have used 3M 4200 with excellent results for thru hulls. Doesn't have the nasty adhesion of 5200.

Yes 3M 4200 & 3M UV400 are both about half of 5200 at roughly 300 PSI adhesion. For me personally, I still think 300 PSI is over kill and that is why I used to use 3M 101 which was 130 PSI and now will use Sika 295 UV (160 PSI), 201US (175 PSI) or 291 (220 PSI). I may even go back to Life Calk..

 

[Rick D]

...and Life Caulk doesn't harden in the tube...

 

[Jalepeno]

What do you recommend for installing Beckson PO512-WS-10 plastic ports? The instruction only recommend pure silicone. Would Silka 295UV by a good/better alternative? I used Silka 295UV to bed acrilic fixed portlights last fall.

 

[Maine Sail]

What do you recommend for installing Beckson PO512-WS-10 plastic ports? The instruction only recommend pure silicone. Would Silka 295UV by a good/better alternative? I used Silka 295UV to bed acrilic fixed portlights last fall.

Beckson ports and acrylic or polycarbonate are appropriate uses for silicone. I prefer Dow Corning 795. Silicone is what you want to use on Beckson ports.

If you are replacing a Beckson port previously sealed with silicone you'll want to tape around the perimeter first then remove portr and remove as much silicone as you can. At that point you'll want to judiciously sand the bonding area to 100% remove any silicone contamination of the gelcoat. Nothing eats silicone off of or out of the pores in gelcoat. When you think you have it clean enough pur water over it. It should sheet not bead. If it beads you still have silicone contamination. Any left over silicone will prevent a good bond of the new silicone..

You should not use a polyurethane or polysulfide sealant on Beckson ports..

 

[Tim R.]

Another tip to detect silicone is to rub your finger over the area. Nothing sticks to silicone except for dirt.

 

[Jalepeno]

Thank you for the info.

 

[kenn]

What do you recommend for installing Beckson PO512-WS-10 plastic ports? The instruction only recommend pure silicone. Would Silka 295UV by a good/better alternative? I used Silka 295UV to bed acrilic fixed portlights last fall.

As per Don Casey, silicone is a gasket material, not a glue, so you have to install it in a way that will ensure enough material is present, and that it's under mechanical compression. It's not wise to rely on the silicone bond for any mechanical strength.

Last spring when I remounted our side windows using silicone, I used toothpicks to space out the window from the hull about 1/16" and just snugged up the screws to the toothpicks. After letting the silicone cure for a few days, I removed the toothpicks and tightened all the hardware to clamp down on the silicone "gasket".