Catalina 30 Window Leak Repairs

Some owners have completely replaced the rubber(?) gasket that beds the window glass in the aluminum frame. Here is the source of the correct material:

D752C 3/16″ Glazing Vinyl 100′
C.R. Laurence Co. Inc.
P.O. Box 21345
Los Angeles, CA 90021-9989  tel. # 800-421-6144

Note: The above company manufacturing the vinyl glazing insert for the older C30 windows will sell only to dealers.  Weekend’R Products is set up as a dealer, so owners can email Ken for the material. website  Email

Simple Fix:
Most leaks occur because the seal between the outside frame and window glass has separated. Make a cut in the seal and you can most likely pull the old seal out. Scrape all remains of the old seal from the window and from the inside of the frame (it’s not easy to get inside the frame). Clean with acetone or VC thinner, etc, don’t forget to wear gloves and goggles, then clean again and make sure the channel is dry. Mask window glass and frame and apply your new seal. Type of sealant is discussed in the Complete Fix.

If you find your window needs to come out, remove the inside aluminum trim ring and get ready to push the window out. If you are doing this alone, tape the window to the cabin top so it won’t fall out into the water. The only thing i could add was to use a hair dryer on the aluminum frame for several minutes. This warms and  softens up the old sealant and makes the window easier to remove from the cabin top. I was able to remove the windows in about 10 minutes! I was cautious about the amount of heat applied, hence a hair dryer and not a blow torch! Start pushing one end of the frame out easy until you feel the seal between the cabin top and window frame start to separate. If it does not want to come out, move to another spot…just keep going around. A person on the outside can use a razor knife to help break the seal as you push. As it begins to come apart, start moving around the window pushing it out easy. Just keep pushing all the way around. Don’t be in a hurry and don’t push or pull too hard or you may bend the frame and/or break the glass. The first one I did seemed like it would never come loose! I was about ready to kick it out, then all of a sudden it started to come out! So nice even pressure all the way around.

The Complete Window Fix:
Figure out the source of the leak…
Is it the seal between the aluminum frame and fiberglass cabin top, or the seal between the aluminum frame and glass?
If it’s the cabin seal, water will drip off the underside of the inside frame, or run down the fiberglass hull liner below the window, or at other locations like that. It should not be wet inside the frame channel if you pull off the rubber trim molding around the inside of the window frame. If water accumulates in the channel for the trim molding, then it’s likely the glass-to-frame seal that is leaking. Sometimes they both leak.

To fix the glass-to-frame seal leak:

1. Window in or out?
This can be fixed with the window on the boat, but I find a better job is done working with the window removed. Be careful that when you push it out, it stays on board (if you remove the window, it means you will have to replace the hull-to-frame seal also).

2. Remove the old seal.
Cut very carefully around the whole glass–right along the aluminum frame–with a razor knife or X-acto knife or similar to remove the old silicone rubber seal (that is probably now somewhat cracked, hard, and gray).

3. Cut at an angle into the joint so the new seal will have as much “depth” as possible. Also cut with your blade lying flat against the glass to break the seal along there. The old seal will pull out. Clean up anything remaining with a razor blade, etc., to get all the old seal off the glass and frame.

4. Preparation.
Clean everything well! Solvent, alcohol, ammonia, glass cleaner … make sure it’s all gone and there’s no silicone or dirt residue left.

5. Replace the seal.
Use a good product — clear Marine-grade silicone. Use the ammonia-based rather than acid-based kind (the vinegar smelling stuff is acid based). Life Seal makes an ammonia-based silicone. Don’t scrimp–marine silicone has mildew control and is better at UV resistance than home-use silicone.

~~NOTE– a recent Sailnet email discussion list post mentioned using a “clear” polyurethane auto window sealer/adhesive available from NAPA dealers in a caulking tube. Sounds like a winner because it’s formulated for such use.~~

I find I need more than one of the individual squeeze tubes, so I get the large caulking tube kind — it’s more economical. Run a bead down in the cutout to replace the old seal. Angle the tube and head so it forces the goop down inside the cutout space. Let it set up well before replacing the window (if possible). Check for rain clouds — a thunderhead is probably moving in by now.

6. A nice edge? (here’s where there’s dissension as to the best way)
A. Lay a strip of masking tape down so you can end up with a neat edge along
the glass side.
B. Use a wooden popsicle stick, plastic blunt item (spoon?), even your finger — wetted with water so the sealer won’t adhere. And run it around to make a nice smooth, even seal.
C. Whatever works for you to get a job you’re happy with.

For Frame to Cabin top Leaks:

7. Remove the window and frame from the hull.

8. Remove all the old mastic from both the cabin top fiberglass and the aluminum frame.

9. Clean, clean, clean it. And clean it again. I find a harsh solvent like acetone or VC thinner works to get at the mastic. Physically get as much off as you can <<physically>> — before you go the solvent route to finish up. It gets messy and it’s nasty stuff, so why use more than you need to? Don’t forget to wear gloves and goggles.

10. Clean it again.

11. Check the frame for straightness… a bent frame will more likely leak again. Put the window in the opening to see how it fits against the cabin top. Are there gaps?
As a guide, mark the outside of the cabin top lightly with a pencil around the frame, or at the corners so you know where the frame fits in correctly. Typically there is a lot of play when refitting the frame into the hole. You want to get it right the first time — not reposition it. Can you do this before you take the window out? (Yes, but the thinner and cleaning will remove most of your marks).

12. Replace the seal.
A. Lay a butyl rubber seal onto the back side of the frame. You can get a big roll at your friendly RV dealer for about five bucks or so. It’s used for setting RV windows and the like, just like on your floating RV. It comes in both black and off-white — with the white being a little more “sticky,” flexible, and easier to use, I find.
B. LAY the rubber in — DON’T stretch it in place as you place it. You want as much body to it as possible. Pulling and stretching it onto the frame will end up with a thinner seal with less butyl “meat” to seal the joint.
C. Make the butt joint for the butyl rubber seal at the BOTTOM of the window. Just butt the two ends tightly–don’t overlap the rubber. Make the seal just a LITTLE too long so when you butt them, there’s a little pressure holding the two ends together.

13. Replace the window
Go for it. Put ‘er back in place and evenly take up on the screws to seat the rubber. Don’t distort the frame, just an even pressure all around.

14. Finish off –  Now here are some more options…
A. Let the butyl rubber set overnight and wait to pull off the excess that oozes out around the frame outside. It’s best done when it’s cool weather outside. I can usually pull (“snap”) it off from the cabin top with a quick, jerk-like pull (okay, no comments required here from the peanut gallery). I have also used a sharpened wooden stick, plastic putty knife–or whatever–to cut the rubber around the aluminum frame. –or–
B. Immediately carefully trim the excess off with a razor knife or X-acto

The Compete Fix comes to us from Ken Kloeber of Boston, NY. Ken sails a C-30 TR, Positive Impact on Lake Erie out of Buffalo, New York. If you have any questions about the fix, contact Ken through his website at