Caulking Cockpit Floor - LifeCaulk over Butyl Tape?

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Pat Anderson

New member
The first step in the gas tank cleaning was taking up the cockpit floor. Now I have cleaned the old caulking off the boat and the cockpit floor, and am ready to put the floor back down and re-caulk. That got me studying potential caulking, since the old stuff was FAR too adhesive and hard to get up.

There is a large gap all the way around the cockpit floor. I don't want to fill that gap with anything adhesive or hard to get up. Butyl tape seems to fill that purpose nicely, since it seals well, stays flexible and has low adhesion. But for appearance, I am thinking the top part of the caulking should be something like LifeCaulk, maybe the top quarter inch or so.

Anybody see any problem with that approach?

Here is short video on butyl tape, and Dicor butyl tape is available on Amazon. Dicor is a leading manufacturer of sealants for RV, so I know it is a good brand.

 
Pat, I used 3M 4000 when I removed/replaced the cockpit floor. It stays white. I think I used 3 tubes. Sets quickly, so it's best if 2 people do it, one to apply, the other to smooth. The second person needs a trial run.

Boris
 
I'm a big fan of butyl, but I wouldn't use it in most gap-filling scenarios. It stays very soft and sticky (its good point) but that would make it a big mess in an application with gaps, and it doesn't have its own "structure," if you know what I mean. (If it's a captured gap, such as a pocket under a plastic/geometrical frame, then maybe.) Also, I don't know if fuel ever makes its way to that area, but it is not fuel resistant at all (why it cleans up so easily with mineral spirits, even years later).

Since I can't see the gaps or exactly what you have there, I don't feel confident in making a suggestion, but butyl probably not. (OTOH, if you were using butyl for something/else, there is no need/desire to go over it with anything other bedding compound or caulk, IMO. If you need another compound, then just go with that through and through.
 
I agree with 4000 as being one of the good sealant/adhesives. The butyl tape has to be in compression--kept tight between screws. As Sunbeam says, it is not for filling gaps.

Yes, Boat Life Life seal would work, and in this case may actually be the preferential material.

Here the product description:
A unique combination of marine silicone and polyurethane, formulated especially for fiberglass. LifeSeal® offers a fast-curing, low odor, high adhesion, non-sagging, non-corrosive, non-yellowing formula. It provides a durable permanent watertight seal for joints subject to structural movement. May be used above and below the waterline. Use for sealing decks to hulls, thru-hull fittings, vinyl ports, sealing/glazing windshields and bedding marine hardware. Will adhere to metal, glass, wood, Lexan®, ABS® and certain other materials. Can be removed without damaging gel-coat.
Click to expand...

It is one of the fuel "Silicones" which is useful in boating. It is also preferential for use of bedding plastic fittings, such as plastic port holes.
 
What is WRONG with LifeCaulk (and probably 3M 4000) for filling the large voids between the cockpit floor and the boat is that it is "high adhesion." I don't think anybody appreciates how LARGE that void is. What I need is LOW adhesion, so when it needs to come out again, if ever, it will not be the total PITA that I faced for two days trying to remove the old caulking, whatever it was. We need something to fill a fairly large void between the cockpit floor and the boat that would NOT be hard to remove. I still don't understand why butyl tape pressed down into that void to mostly fill it would not fill the bill better than anything else, since it stays flexible and is low adhesion. What am I missing?
 
Pat, do you want water getting into the gap, and possibly getting trapped around the "bulkheads/stringers"?

There are some silicones which are very high adhesive value, and some low adhesion. Silicones do penetrate the gel coat, and make adhesion of other products more difficult down the line.

There is a reason that the factory used the material which they used. That was to keep water out. laying butyl tape in the "groove" , it will not be under any compression, and thus no adhesion--and water will get in there. Once in there, because of the nature of the construction--it will be difficult to remove.

Your choice.
 
To remove adhesives/sealants (several types,) I've used DeBond Marine Formula. This "removes polyurethane adhesives and sealants including cured and uncured 3M™5200, 4200 and 4000 & Sika™ 291 adhesives". It works.

A similar product is: "BoatLIFE Release Sealant & Adhesive Remover.
Ideal for Removing Cured Silicone, Polyurethane, and Polysulfide.

Boris
 
BrentB":1rpsv8og said:
How wide is the gap?
Click to expand...

I will take a picture when I drop the floor back in before caulking. The floor is actually quite a poor fit, and the size of the gap varies significantly around the floor. I will also measure the depth.

I have four tubes of Boat Life LifeCaulk, and am dubious whether that will be sufficient, but we'll see.
 
Pat Anderson":dgrjphpu said:
The floor is actually quite a poor fit, and the size of the gap varies significantly around the floor.
Click to expand...

I'll be interested to see photos. I was thinking you were bedding the hatch but now it sounds like it's maybe the whole cockpit sole (?).

If you have something like a sole to ledger fit that is something that will always be there, and it is a very poor fit with gaps, you might consider molding an interface of thickened epoxy. We used to do this before re-installing keels that had poor fitment. Basic idea is that you tape one surface with something like shiny/clear packing tape (so that nothing will stick) and prep the other surface for epoxy to stick to it. Then you slather the prepped surface with thickened epoxy and place it how it ought to go permanently. Once the epoxy cures you separate the two pieces (which the tape allows) and remove the tape, then use bedding compound or caulk to re-install "permanently" -- you now have a more-or-less perfect fit this time, and any future times, and the bedding compound is doing just that - bedding - vs. major gap filling (which tends not to work in the long run).

Of course I may not be visualizing what you are doing correctly - photos will likely clear that up.
 
In thinking about the cockpit floor, I would like to point out that the tank is open to the aft lazaret. There are drain holes, right at hull level which serves to drain water from the tank compartment to the lazaret and vice versa.

Where I'm going with this is that even if you seal the cockpit floor tight, water will get in the aft of the boat through the floor hatches. When you drive the boat, or otherwise get it to a position of bow down, the water goes directly around the tank. Fresh water, perhaps, but water nevertheless. Pumping the aft lazaret helps, but remember to drain the aft section of the boat via the drain plug.

Boris
 
journey on":34zticft said:
To remove adhesives/sealants (several types,) I've used DeBond Marine Formula. This "removes polyurethane adhesives and sealants including cured and uncured 3M™5200, 4200 and 4000 & Sika™ 291 adhesives". It works.

A similar product is: "BoatLIFE Release Sealant & Adhesive Remover.
Ideal for Removing Cured Silicone, Polyurethane, and Polysulfide.
Boris
Click to expand...

I wish I had one of those products BEFORE I started! I used Goo Gone, effective on some stuff to soften,m totally ineffective on other stuff.

 
Sunbeam":3844lnxw said:
I'll be interested to see photos. I was thinking you were bedding the hatch but now it sounds like it's maybe the whole cockpit sole (?).
Click to expand...

There are two related projects. The whole scope is kind of in two threads, this one and GOOD SERVICE - Fuel Tank Cleaned and Access Port Installed... To access the gas tank to put the access port in, the cockpit floor (sole?) had to come out. That was difficult because the prior sealer around it was highly adhesive, and very difficult to remove. I got it, or most of it, but a lot of cursing was involved!

The related project is to install a new hatch to replace the inspection port to get to the gas tank access port and fuel gauge sending unit. The original inspection port was over...nothing, somehow the tank guy and the inspection port guy in 2005 were on different pages. The hole for the hatch has been cut in the cockpit floor, which is still out of the boat. I just finished routing out the areas where the hatch screws will go and am about to start putting thickened epoxy in there.

When the hatch is bedded and screwed down, I will lay the cockpit floor back in the boat, but it will be a week before I put the four tubes of LifeCaulk around it. The last step will be to reinstall the steps. Yesterday I routed out the rotten wood in the steps and filled them with thickened epoxy.

I am hoping it is a LONG, LONG time before that cockpit floor has to come out again!
 
I have to agree with Boris. Our notoriously wet bilge is open to the fuel tank via at least three openings in the bulkhead between battery/water tank and fuel tank; one to part & starboard and a larger cut out dead center. Whenever we lay the boat up or park it without use, I open all four hatches to let air flow throw and I try to keep the bilge as dry as possible. NOT an easy feat.
 
Pat,
Posting a photo of the cockpit/fuel tank, from the aft cabin bulkhead to the bulkhead in front of the splash well would be a good idea to clarify several issues.

I sent you a PM, about one concern I did not mention on the forum. That is that various boats in the 25 series have been built differently--both from the type of fuel tank (plastic vs Aluminum), fuel fill and vents (one side vs two sides and mid cockpit vs forward cockpit).

Some 25's have had core rot in the aft cabin bulkhead, because water sat under that aft cabin bulkhead, and wicked up into the balsa core, which had not been adequate tabbed into the bottom or the boat, leaving core exposed to the water.
The area under the cockpit floor in the 25 had various "stringers" and "petitions" to hold the fuel tank in place. In some boats, there is a plywood on edge petition between the fuel tank and aft cabin bulkhead. These are glassed over with mat.
Some have limber holes, (to allow water to drain aft) and some don't.

Even though some water will get into the area where the tank is, thru the cockpit floor hatch and access holes, you want to avoid more water getting in from around the edges.--especially trapped around the lower part of the aft cabin bulkhead, causing core rot and in some cases getting into the cabin under the cabinets on each side.
 
We have an aluminum fuel tank with a fuel fill and vent on each side. My vent is like the one Boris described, the vent hole points aft and slightly down. The PetroClean guys said the tank itself was in very good condition. Don't know about the other stuff, I will look closely when I am able. I have stuff in B'ham tomorrow and then will be gone for a week, so it will be the following weekend before I get back to the boat!
 
I just pulled up my cockpit floor yesterday. Easier job than I thought it would be and only took about an hour. After removing the side steps I used a sharp utility knife to cut down both sides of the sealant, then pulled the sealant out. Then used a flat pri-bar to lift the floor out of the rim. Tomorrow I plan to raise the bow some then pressure wash the mold and mildew off the fuel tank and bilge area. Tighten up some ground screws and look into changing out the fuel gauge sender. After that I’ll put the floor in. Sounds like the 3M 4000 is what some are recommending. But would the self leveling RV sealants work? Colby
 
Although some of the sealants like Dicor or Geocel might work, the 3M 4000 would be a better choice (after very thorough cleaning. I have used both of the RV sealants many times. They tend to flow more than the 4000 does.
 
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