Fixing the infamous Catalac Catamaran window leaks

A dry boat interior

To say that I’ve had a problem with my Catalac windows leaking would be the understatement of the year. Catalac Catamarans have had a chronic window leak problem and yes…. my boat is no exception. The leaking windows have been my pet project especially the port and starboard cabin window units. Let me tell you what I’ve done so far, and what works and what doesn’t.

The first thing I did to stop the leaks was to grab a caulking gun and put a bead of latex caulk around the exterior of the offending windows… I was neat and meticulous and very proud when it was done. Until the next rainstorm that is…. the result was no effect at all. Everything still leaked as if I had done nothing at all. Very frustrating ….

Next, I made sure I sat in the boat and forced myself to watch where the leaks were coming from. My girlfriend grabbed a marina hose while I sat in a closed up 100 degree boat and watched…. no leaks at all when hosed down. Again …. very frustrating …

If you’re confused, you should have seen me. But …. I was determined ( some would call this being stubborn)

Finally,  I headed for the boat during a hard rain and found leaks all over the place, and forced myself to carefully study the issue to discover exactly how the windows were leaking. Near as I could tell there were two sources of water. The first, was the glass frame seal gasket. This was dried and cracked. It’s apparent in this photo. 

Knarly old gasket

The other source of leaks on the main cabin window group almost seems to leak by design. The track at the bottom of the window is shared by the entire group. The removable window, allows water to collect in this bottom track. It has weep holes which are supposed to drain it out, however, if those weep holes are blocked the water migrates down the track and fills up the downhill window track which then begins spilling it in the interior of the boat. It was obvious that part of normal maintenance was to keep these weep holes clear.

Now that I had the problem in hand, I came up with a Plan A and Plan B. 

1.) Plan A was to replace both the inner and outer window seals on the large forward cabin windows without actually removing the windows. It doesn’t appear necessary to disassemble the entire window group and actually replace the interor and exterior gaskets with another gasket. Marine formulated caulk will bond to glass and aluminum just fine as long as the surfaces are clean. This procedure should reduce the repair time, and eliminate boat yard costs as it can be done while the boat is in her slip and modern caulks will last 30 years.

2.) Plan B was to unbolt the main cabin windows, bring them home, disassemble them and replace both the inner and outer gasket. After thinking about this for a while and really looking closely at how much trouble it was going to be to remove the entire window group … I decided plan A was the way to go with all the windows in the boat. Also,  I’m not aware of any marina that is comfortable with an owner disassembling his boat while in a slip. So, this meant implementing Plan “B” would result in an expensive haul out and utimately I figured Plan B was too much work and expense. I figured that if I tried Plan A on all the windows, and it failed, I could always fall back on good ole plan B.

It’s time to talk about sealants. I selected 3M 4200 quickset. (3M 4000 will also work) It’s messy but will last 20 years (I’m sure not planning on doing this again). This stuff has it’s good and bad points. It’s the messiest ‘goo’ I’ve ever used, but it sticks to everything. and is removeable. 

I set out on “Plan A” basically using three tools. The first was my cordless Hi speed drill fitted with a Nylon Brush attachment. This attchment looks exactly like the wire wheels you can buy as a drill attachments, but instead of steel, it’s nylon. Another important tool looks like a small ice pick with the tip bent 90 degrees about 1/2 inch from the end. I found this at a Harbor Freight store for about $1.00. 

removing the cracked gasket

Lastly, a common 2″ putty knife.

I began on the interior seal. The drill/ nylon wheel positively destroyed what was left of the exposed glass to frame seal. This appears to be the remains of a 22 year old gasket. I did this project one window at a time and was able to remove the interior seal all around the window to a depth of 3/8″ (10mm).  This procedure will leave a bit of the old gasket deep in the channel, yet I found this useful as it still positioned the glass pane firmly in the aluminum frame. I then used the pick (see photo) to clean up the rough spots so there was a clean channel all the way around the aluminum frame.  When using the Nylon wheel, it’s important to angle the drill so that the metal hub doesn’t touch the window.  Once that was done I washed out the window channel with water, allowing water to get into the now wide open seal and wash the old gasket bits out. 3M 4200 requires clean surfaces to bond to the window and a small amount of water which remains in the channel actually helps the 4200 sealant to cure.  I can’t say this strongly enough. We need clean surfaces for the caulk to stick to the frame and glass.

replacing the gasket with caulk

I grabbed some painter’s tape and ran it around the glass perimeter, This greatly reduced clean up time. I then utilized my best tool ( my fingers) to smear caulk into the gap and push it down. It’s important to use the putty knife to push it in deep and then refill the gap until it was even with the edge of the aluminum channel. I started at one end of the track and worked slowly until I had one edge of the window completed. I did the same around the entire window and then immediately smoothed this line of caulk with a cloth wet with mineral spirits, smoothing it flat and then removed the tape (which is impossible to do once this caulk is dry). This not only removes the excess caulk, but smooths the new bead of caulk so it looks prfessionally done. Don’t worry about having a sparkling clean window at this point, just get the goo off. When completed, move on to the next window. When done, I repeated the procedure on the outside of the same window.  When finished I had 1/4 inch bead of the best marine sealant around each window, inside and out.

A quick note about the inside project, my main cabin window groups have rubber corner pieces in each interior corner of every fixed window. I removed these before I started and tossed them into a pail of water to soak. When the soaking softened the old caulk stuck to them, I cleaned them up with a wire brush and mineral spirits. Then using latex caulk I placed them back into their tracks putting extra caulk around the pieces that border the removable windows. When the caulk cures, simple glass cleaner is all that is needed to finish the job.

In conclusion.. this procedure works (I have had no window leaks where ever I performed this repair) and I never needed to resort to “Plan B”. Although I will admit that this is a very time consuming and messy job.

I hope this page will be of some use to Catalac owners. Use the contact form to email me with any specific questions.


By Rick

Owner of a Catalac 8M and Catamaransite webmaster.

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