Removing silicone from outer cabin

I recently purchased a '76 Ericson 27, on which the portals had been replaced with excessive silicone sealant on the outside of the cabin. I have tried to gently scrape it off without damaging the finish, but is not working. Any suggestions on how to remove it? Would a synthetic scrubbing pad damage the finish? Appreciate any suggestions.
Thanks.

Two things. First is that solvents won't dissolve silicone, but they can soften it by absorbing into it. Haven't seen it recently, but there used to be a silicone caulk specific solvent out there. I would try wetting the mess with toluene or xylene to first soften it. Wear gloves with that stuff, and don't do it indoors (but you knew that).

But even with it softened, you will still have to scrape it off. For that the best thing I know of is a flat razor blade (the single edge type) that has been dulled a bit with sandpaper, used almost flat against the surface. A fresh sharp blade will catch on the surface and scratch it, but if you blunt it a bit, especially at the corners, it will slide along the fiberglass surface without catching it, and allow you to lift off silicone or varnish or the like.

Boatlife caulk remover claims to remove cured silicone, but I've never tried it.

I use a small pull scraper. Works great on flat surfaces. Do it with dirty hands as you can rub your fingers over the silicone and the dirt will stick. Then you will know when it is all gone. I hope you are not planning on painting this area.

3M Adhesive remover works great on this. Use a hard plastic putty knife or plastic blade scraper and you wont tear up the gel coat. Razor blades and metal scrapers work but almost always end up leaving scratches.

It's long and slow....

But I have been using a rough piece of turkish toweling (read...VERY CHEAP) saturated with denatured alcohol.....

It is slow...but it works....really cleans the surface when you get it all off....

The plastic scraper will get the bulk off...but the final cleanup is what I think you are really interested in.....

Good Luck

IMHO Silicone has *nearly* no place on a boat. Its just such a pain to remove, and nothing sticks to it.

Ok, I'm done ranting now.

Silicon Remover

I have been using a nylon abrasive wheel with weed wacker type tines to
remove silicon caulking. They come in #80 and #120 grit.
Super handy for getting things out of cracks and they do not mar fiberglass.
I remove as mutch as I can with a razor blade scraper first. Final cleanup with
acetone. Silicon has very few uses on a boat other than piping sealant
Stay away from using it as caulking. Sika Marine Caulking is my choice for
exterior fiberglass caulking to stainless or wood. 3M 5200 Adhesive is my choice for Hardware imbedment on deck :nerd:

Happy Sealants

When you think...

When you think you have the silicone cleaned off spray some water on the area as a final test. If it beads, which it likely will, there is still silicone and the only sure fire way to remove it is by wet sanding...

For me there are two sealants that have no place or very, very limited use on a boat and those are Sikaflex 292 (Sika's version of 5200), 3M 5200 and any product containing silicone including Life Seal (polyurethane/silicone combo product)..

Your polyester hull has a peel strength of roughly 400 to 500 psi why use a product like 5200 with a 700 PSI peel strength?

Nothing on a boat is permanent. 5200 is actually more permanent than your gelcoat! Think about it..? Try Sikaflex 291 (medium bond strength polyurethane), 3M101 (medium to low bond strength polysulfide) or 3M 4200 (medium bond strength polyurethane)...

Life Calk has no silicone

Maine Sail said:

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For me there are two sealants that have no place or very, very limited use on a boat and those are Sikaflex 292 (Sika's version of 5200), 3M 5200 and any product containing silicone including Life Caulk (polysulfide/silicone combo product)..

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Life SEAL is the silicone and polyurethane combo. Life CALK is the straight polysulfide, better for bedding and for things that will be removed. Polysulfides are not good for most plastics, but are compatible with fiberglass, glass and metal.

They're easy to confuse. Both of those products are from Boatlife and have the same color packaging, so make sure you get the right stuff. I like the polysulfides for bedding deck hardware and ports. I try to stay away from silicones, too. I don't know enough about polyurethane to say when it should be used, or if it's better for certain applications.

footrope said:

Life SEAL is the silicone and polyurethane combo. Life CALK is the straight polysulfide, better for bedding and for things that will be removed. Polysulfides are not good for most plastics, but are compatible with fiberglass, glass and metal.

They're easy to confuse. Both of those products are from Boatlife and have the same color packaging, so make sure you get the right stuff. I like the polysulfides for bedding deck hardware and ports. I try to stay away from silicones, too. I don't know enough about polyurethane to say when it should be used, or if it's better for certain applications.

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Yeah my bad! I ALWAYS confuse the two. With numbers it's easier not to as in 5200 / 4200 but Life Caulk/Seal is easy to confuse. I guess it's easier to say don't use the Boat Life product that is combined with Silicone..

For bedding chainplates, which flex and move a bit, what do you guys use? What is more flexible, polysulfide or polyurathane? Which stands up better to UV degredation? Once removing the old bedding, an recommendations of which solvent to prep the serfaces with before rebedding?

My 38 has U-bolts and an above deck steel plate and I used Life Calk polysulfide for the bolt shanks and under the plate. I've only done the center pair on the starboard side, because the others are OK so far. I do not know which is more flexible. I used 4200, which is polyurethane based, to re-secure some 1 inch diameter three strand manila rope to the gunnel of my dink and I think it has stayed flexible. If you search this site you'll find some that use 4200 for bedding and some that use the polysulfide.

ChrisS said:

What is more flexible, polysulfide or polyurathane? Which stands up better to UV degredation? Once removing the old bedding, an recommendations of which solvent to prep the serfaces with before rebedding?

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It's a tough question but here re some things to consider:

1) Polysulfide is used for teak deck seams and it will handle UV better than a polyurethane.

2) Polyurethanes have greater "elongation before break" but over time will harden thus reducing their "elongation at break" claims where polysulfides don't generally harden nearly as much over time.

In my experience the polyurethane sealants continue to harden until they become almost brittle (takes a while though) and polysulfides tend to stay rubbery for the duration depending on UV exposure.. My Take, from years of experience, is that in 5, 10 or 20 years the 3M 101 polysulfide will still be very close to it's 416% elongation at break/flexibility and the 5200 or 4200 will potentially be less than that of 101 given nature of polyurethanes and how they continue to harden/cure over time. Keel joint leaks are an example of polyurethanes hardening over time that come to mind. I'd still use a polyurethane for a keel joint but they do harden eventually and lose flexibility.
Here's a summary of the products in the 3M line:Elongation at break and tensile/grip strength:

3M 5200 = 1350% Tensile Strength = 700psi
3M 4200 = 900% Tensile Strength = 300psi
3M UV4000 = 800% Tensile Strength = 300psi
3M Silicone = 350% Tensile Strength = 220psi
3M 101 = 416% Tensile Strength = 139psi

Keep in mind with polyurethanes that these elongation at break numbers take a best case scenario and that number will generally diminish over time..
Some additional things to consider:For some strange reason I don't find the BoatLife polysulfide as long lasting or flexible in the long term as the 3M 101 polysulfide yet they are both derived from the original Thiokol. I don't know what to attribute this to..
4200 is a fine product but it can still be a bear to remove compared to 3M 101. I've tried UV4000 but don't like the clean up and it turns yellow so it's really not all that "UV"...For chain plates Sikaflex 291 might be a good happy medium. It has a 600% elongation at break but only a 200 PSI peel strength so it's easier to remove in the future than 4200 but harder than a polysulfide..

The bottom line is that the bigger the "gap" around the chain plate the more flexibility you'll have no matter what the sealant.

500% of 1/32 of an inch is a lot less allowable movement than 500% 1/8 of an inch. Sure it's still 500% but your allowable movement or flex is going to be considerably more with a bigger gap or sealant bead. This is why you should countersink bolt holes under hardware as it gives a 1/16 to an 1/8 of an inch of sealant bed flex vs. 1/64 or 1/32 without countersinking...

Acetone or Xylene work well to prep the surface once ALL old residue or remnants of silicone are gone..