Varnish Round II and Cockpit Work

I started the day with by varnishing all the pieces I had done yesterday.  Here’s a photo of the varnished pieces:

Making progress.  I'm happy with how the engine compartment is a similar color to the teak.

Making progress. I’m happy with how the engine compartment is a similar color to the teak.

After setting them out to dry, I got out my tools to dig silicone sealant out of the cockpit edges.

Silicone is awful stuff.  It has only one or two applications for boats, but many boat owners use it for everything.  My new Grey/Pomponette opening ports called for silicone sealant for installation, and it has been okay.  It’s also okay for sealing plexiglass and real glass – if you use the marine formulation and not the stuff you get at Home Depot.  There is a significant difference between the two products. However, that’s about it.  It’s not good for mounting hardware, sealing screws, chain plates, fittings, through-hulls – especially beneath the waterline – it doesn’t make a reliable seal for anything but glass, plexiglass, or those ports I mentioned.  And it certainly isn’t appropriate for sealing the edges of a cockpit sole.  Why?

Silicone doesn’t really, really stick and seal to most surfaces.  However, it seems to be impervious to any solvent.  It leaves a residue that doesn’t seem to have any solvent.  So when you want to get it off a surface, the surface has to be scraped down to new material.  Silicone contamination prevents anything else from sticking to a surface where it’s been.  Try painting a surface that’s contaminated with it – you will never get the paint to perform correctly in that location.  Frustrating!  I know of people who say it’s useless, or worse:  it’s pure evil.  I don’t think it’s useless, but it is one of the most mis-used materials on boats.  Okay – back to my cockpit sole:

When the core of the cockpit went soft, a previous owner had the sole repaired by laying a piece of 1/2″ marine plywood on top of the original sole, glued down with 3M5200, then unaccountably sealed the edges with silicone.  I still don’t understand – he glued the sole down with 5200, but sealed the edges with . . .   Anyway, the edges leak, of course.  It’s not a steady stream, but a fair amount of water gets below with each rain.  Today I took a deep breath and started excavating silicone.  I used razor blades and box cutters, flat-bladed screw drivers, chisels, and various other tools.  The one power tool – the most effective tool I used – was a vibrating tool with a scraper blade.  It still took a lot of effort and time, but I got out much of the old sealant, and scraped a lot of the surface.  It wasn’t a perfect surface preparation, because I’m not sure that’s even possible with silicone contamination, but I got much of it, and much of the residue.  Here are few photos of the edges with all the silicone dug out:

Look closely - there is still silicone down there.  How do you get all of it out?

Look closely – there is still silicone down there. How do you get all of it out?


I had resealed the back end of the floor when I first bought the boat, so only had to go around three sides.

Here’s a photo of it sealed with 3M 4000:

DSC_2116Here, I had a foolish sense of economy for some reason – not really rational, but I guess I was just smarting from having to pay nearly $20 per cartridge for this stuff.  I used one whole tube to get round the three sides, and had another in reserve.  I think it’s all sealed okay, but I wish I had used much more sealant.  That’s the rule, you know:  Use much more sealant than seems reasonable, and it will then be well sealed.   If you try to economize with the stuff, you may not get a good seal, and you’ll have to do it all over.  I hope I used enough . . .

  1. You may not be aware of this but silicone is a lubricant. The sealant stuff is designed to mimic silcone rubber that are ilk O rings and gaskets you see on many things. However it comes out of a tube so not everything gets mixed as well as it should and it cures unevenly. However if it adheres(questionable) then you have a nice slick gasket which will seal if compressed. This is why nothing sticks to the residue. It is also part of the reason it is hard to get off a surface because if it actually adheres there is little that can harm it. Of course 5200 has it’s problems too. Did you know it has one of the highest strength bonds of Anything made! Somewhere around 4000 lbs per square inch of holding power. But 3M does make a solvent for it so you can remove it, it is just expensive. Imagine how thrilled I was when a guy offered up 11 tubes of a twelve tube case on CL here for $30.00. Yeah they were out of date and I did have trouble with one tube. The rest worked like normal. I am using them against a concrete block wall as sealer and adhesive for wood being mounted on the wall. Plus I might seal some thin cracks in the wall with it, maybe. The wood is really staying on the wall!!

    • Allen, I think I was aware of silicone’s lubricating properties – you can get a silicone spray that is used to keep gaskets supple, and I’ve used it for that in cars before. I know, as you mentioned, that you can build a gasket with it, and that is a good application in some circumstances. And of course, 3M 5200 is a permanent adhesive – that’s why I chose it’s lesser permanent cousin 4000. I am aware of the proprietary solvent for 3M products – I just wish there was one for silicone :-).

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