Sealing Cockpit Floor / Engine Bay Roof Hatch

[SVJOCO]

There is a big bead of some kind of sealant around this hatch, and it is leaking in multiple spots, so I need to reseal.

What is the right product (sealant type & perhaps brand) for the task?

Any tricks for removal of the old seal? I have the sealant cutting attachment for my multitool and then I figured a utility knife and finally acetone before resealing.

All help appreciated! I love this forum.

Cheers,

Jeff

[tkeithlu]

It looks like mouldy old silicone sealant, and looks like it is meant to be opened on occasion. Your utility knife may be the best instrument of attack, and you may find that it peals loose once you separate the parts. That situation means don't use something really permanent, such as 3M 5200, but silicone sealant instead. If you look at several types you will find a rating in number of years expected life. Go to the 30 years or more types. That's really a measure of the amount of water in the goo; less water means less shrinkage and longer life. Some of the specialists hereon can name favorites to try.

[chowdan]

That looks similar to my cockpit floor design. The previous owner had the original engine pulled and a larger one installed. The only way the engine goes in or out of the boat is via the cockpit floor.

As for sealing, mine is bolted down and typically I'd say use something like Butyl tape, but considering it is not good if it gets in contact with fuels and such. When/if I have to pull mine, I am planning to use either 3m 4000/4200(UV stable variant), or Sikaflex. You do NOT want something that is an adhesive of as it will make your life a bit of hell if you have to remove in the future.

5200 should go to hell.

[SVJOCO]

Thanks guys.

Anyone else have a suggestion to add?

[wingssail]

Originally Posted by SVJOCO

Thanks guys.

Anyone else have a suggestion to add?

The good news is that it is apparently bolted, so the sealant only has to seal it, not hold it in place.

Cutting around the edge with a carpet knife then carefully prying it up will get it off. Then you can peal or scrape most, if not all of the old sealant with a putty knife.

Clean both the hatch and the deck and use acetone to get everything off, but be careful if the hatch is plastic, the acetone will damage the finish, use alchohol.

Tape the boat and the hatch with masking tape, (I use blue). Put a sufficient bead all around then screw down the hatch lightly so as to not to squeeze out all the sealant. Using a wet finger smooth and finish the bead. Pull off the masking tape before the sealant is cured and you will get a nice edge.

After the sealant is hard you can tighten the screws.

I too use 3M 4000UV.

One caution, if the hatch is plastic it will have a high coefficient of expansion (temperature) and if it is hot when installed it will shrink when cooled, breaking the seal to the plastic. It is better to install it when everything is cool. The expanding plastic on a hot day will compress the sealant which is better withstood by the sealant's adhesive.

If you got to a tropical climate be careful of Butyl tape, it can run like pine pitch when hot.

[s/v Jedi]

I had the same problem, used 4000UV which failed within one year. Word was that 3M had formulation problems with the product. I lost all confidence in it. In the end I checked that the gasket was still there, then filled the opening with epoxy. The chance that the engine needs to get out is small and then I’ll just grind the epoxy out. No more leaks

[boden36]

I have always used a neoprene gasket with plenty of Butyl Mastic sealant. Works well and easy to remove.

[SVJOCO]

The panel was held down by bolts that thread through the deck and access panel, no nuts on the back side.

Now that I’ve removed the panel, it appears a 2 step approach was taken previously. It looks like Life Caulk was used directly where the hatch is held down (darker blue in the photo), and then silicone was used to fill the gap around the panel to bring the gap level with the panel surface.

To get the panel up I had to go in the hallway beside the engine bay, lay on my back, and use my legs to push up on the panel at one corner. There is no way to grab the panel at the top because the gap is too narrow. Because of this I’m concerned that if I put this all back together with 4000uv , I’ll never get it off again. Is my hunch correct? (I’ve never used 4000uv, but looking at specs it might be difficult)

Is my best bet to reseal this setup completely with a polysulfide like Life Caulk? Sika 295 looked decent also but isn’t immediately available to me here.

[gonesail]

why not try butyl tape?

[SVJOCO]

Originally Posted by gonesail

why not try butyl tape?

Because of the bolts turning and messing it up; I can’t pull it down without turning the bolts. Also, what to put around the hatch to bring it level? (important for drainage in this instance because the water needs to flow out of this section and aft past the pedestal.)