Refurbish Deck Caulking

[einspritzer]

I just got an OUTRAGE 18, a boat I have always wanted. I have several projects planned to clean up the OUTRAGE. My first project [will be two projects: something unrelated to caulking the deck which needs its own thread] and re-sealing the deck. I've been scraping [out] the old caulking with a knife, and I have [the areas where there was old caulking] clean. I'm not planning to remove the deck. I'm going to pull out [some part of the deck described as] small squares so I can clean there.

Q1: how clean must [the areas where there was old caulking] be before I apply new [caulking]?

Q2: must acetone be used to assure the surfaces are clean?

[Phil T]

After you get the seam clean, mask off both sides and apply a bead of BoatLife Life Seal Sealant.

Do NOT use an adhesive/sealant product. No 3M 4200 or 5200.

https://www.jamestowndistributors.com/userportal/show_product.do?pid=1536

[einspritzer]

Hi Phil. Thanks for the advice. I have some 3M4200. I will exchange it for [BoatLife Life Seal Sealant].

Q3: Why is [BoatLife Life Seal Sealant] better [than 3M4200 adhesive for caulking the seam on the deck]?

Q4: Does [BoatLife Life Seal Sealant] last longer [than 3M4200]?

Q5: [When I seal the] thru-hull drains should I use [BoatLife Life Seal Sealant]?

[jimh]

Q3: Why is [BoatLife Life Seal Sealant] better [than 3M4200 adhesive for caulking the seam on the deck]?

As Phil as stated, products like 3M4200 and 3M5200 are adhesives and sealants. When two surfaces are bonded together with a very strong adhesive such as 3M5200, unbonding and separating the two surfaces will become extremely difficult. Typically to separate surfaces bonded with 3M5200 will require use of a special dissolvant that will chemically alter the bond of 3M5200 to weaken the strength of the adhesion so the bonded surfaces can be separated.

I can speculate that the reason Phil has cautioned you to not use very strong adhesives like 3M5200 as a general caulk is due to the adhesive properties of 3M5200 being so strong.

Boat Life sealant is not designed to be a strong adhesive. It is designed to be a caulk or sealant.

The general reason to not use a very strong adhesive to bond or seal molded assemblies that form the deck of a Boston Whaler OUTRAGE 18 boat is to avoid the extreme difficulty in the future of separating those assemblies if separation becomes necessary.

For a short narrative describing the difficulty in separating surfaces joined by strong adhesives, see

Refitting a Depth Sounder Transducer
http://continuouswave.com/maintenance-logs/newDS/

and, in particular, read the section under the sub-heading "3M-5200: The Right Choice?"

[jimh]

Q5: [When I seal] thru-hull drains should I use [BoatLife Life Seal Sealant]?

For advice on repair of thru-hull drains, please read the FAQ answer at:

http://continuouswave.com/whaler/reference/FAQ/#Q12

For sealing the outward end of through-hull drains that will be underwater, be sure to use a sealant that is appropriate for use underwater.

If you need further advice on repair of through-hull drains or other repairs you plan to perform in the future, start a new thread on those topic so we can stay on the topic of deck caulking material in this thread.

[jimh]

Q1: how clean must [the areas where there was old caulking] be before I apply new [caulking]?

Q2: must acetone be used to assure the surfaces are clean?

A1, A2: In general, in order for a sealer to form a strong, durable, and watertight seal to a surface, the surface should be very clean and particularly free from any oils that could interfere with the bond of the sealant to the surfaces. A strong detergent and vigorous scrubbing should remove dirt. Wiping with acetone should remove any oils or grease that remain after the use of a strong detergent.

[jimh]

I'm not planning to remove the deck.

If you use "deck" to refer to the cockpit deck on an OUTRAGE 18, you cannot "remove the deck." It is an integral part of the Unibond hull. There is no way to remove it from the hull except by destruction of the hull. Typically there are areas of the integral deck which are molded to form cavities for rigging tunnels and for the fuel tank. These cavities are covered by smaller molded parts that are fastened in place with threaded screw fasteners. The largest of these parts is the fuel tank cavity cover. This fuel tank cover is a rectangular part. There are typically one or two other small rectangular assemblies that cover portions of the rigging tunnels. The seams between these removable panels and the fixed deck are sealed or caulked.

[jimh]

For aesthetic reasons, if the boat uses Desert Tan gel coat, a pure white caulk may have too much contrast. Some off-white color for the caulk may be a better match to the Desert Tan gel coat than a pure white caulk. Because residential bathrooms use caulks in areas like showers and tubs, you may find a bathtub caulk that is tinted to an off-white may be a better color match to your boat's gel coat color.

See archived discussions at

http://continuouswave.com/ubb/Forum3/HTML/012947.html

http://continuouswave.com/ubb/Forum3/HTML/017055.html

[floris van den berg]

I just got an OUTRAGE 18...My first project ...re-sealing the deck.

I just finished replacing the caulking on my boat. I think it is important that you will use an UV resistant caulking, (SIKAFLEX 295 UV in white), I have not used any primer so it can be taken out later in case I have to replace it again.

I did clean with acetone. I had "touched up" the existing caulking earlier as a quick fix with non UV resistant caulking, and it will turn yellow.

[jimh]

FLORIS--you make a very interesting point about UV color shift. Thanks for that comment.

Also regarding using a silicon sealant, I earlier mentioned in another thread but will repeat here:

Many silicon RTV-type sealants will create acetic acid as they cure. This can be a problem, particularly around any electrical conductors. Check the sealant composition to establish if it will produce acetic acid during curing.

Here is an excerpt from GE:

What's the difference between GE Silicone I caulk and GE Silicone II caulk?
GE Silicone II caulk is what's called a "neutral cure" silicone, which means no acids are released during the curing process (as there are in GE Silicone I caulk). This enables GE Silicone II caulk to adhere to a broader range of substrates such as plastics, concrete, and metals. Also, the odor of a neutral cure silicone such as GE Silicone II caulk is much less offensive than an acid or acetoxy cure silicone such as GE Silicone I caulk.

And this advice on which type to use for external or outdoor sealing:

Q: What is the difference between acetoxy and neutral cure silicone?

A: As acetoxy cure silicones release acetic acid whilst curing they can cause problems when used on certain substrates. When used on natural stone they can cause discolouration, when used on certain metals they can cause corrosion.....neutral cure silicones have better adhesion and weatherproofing properties compared to acetoxy silicones making them the superior option for external applications.

Cf.: https://www.idealsealants.com/acetoxy-vs-neutral-cure-silicone-i31