Portlight Replacement

The opening portlights on Priorities began leaking when the boat was about 18 years old. The rubber seals had cracked over time and were no longer effective, especially due to the sheer of the sides of the cabinhouse. Actually, the four portlights in the main cabin had been replaced by a previous owner, so problems may have began before I even bought her.

The forward head leaked especially bad, making its shade mildewy, though it at least dribbled into the sink. The aft head portlight caused rainwater to puddle under the toilet, initially leaving a “Uh, what is the puddle of mystery liquid appearing under the hoses of the toilet?” reaction when I first noticed it occurring.

Priorities is a Catalina 400, hull number 53, informally referred to as a “Mark I” after the updated “Mark II” was released in the late 90s. Much (or maybe all) of the Mark Is were equipped with Lewmar “Old” Standard Portlights… 6 opening size 2s forward, 2 opening size 0s aft, and four fixed portlights below the toerail (I think sizes 2 and 0).

Original Lewmar Old Standard Portlight in forward cabin
Original Lewmar Old Standard Portlight in forward cabin

Lewmar changed the design of their “Standard” Portlights in 1997 but kept the name “Standard,” so the two versions are now referred to as “Old” Standard and “New” Standard. The cutout dimensions are almost but not exactly the same, though after replacing 4 portlights on Priorities I haven’t needed to make any modifications to the cutouts in my hull for any portlight. New Standard portlights have an upgraded dogging (or latching) system, where the dogs are pressed to lock rather than twisted to lock. There’s also only one joint in the outer frame rather than two, which probably makes it stronger and therefore more likely to seal.

Replacing the seals in the Old Standard Portlights was something I considered since it didn’t require removing the entire assembly. A new seal and new dogs on each portlight were around half the cost of a new portlight, but still left me with old windows that were starting to craze. Researching online also made me wary of the probability of success I might have when replacing the seals, and I learned it might take quite a bit of time.

My lack of confidence in repairing the portlights led me to replace them instead. Since the new ones were nearly a drop-in replacement, I figured it wouldn’t take much longer (and might be faster) to replace rather than repair, and I’d have a better design with new windows.

Removing the inner plastic trim piece on each portlight was easy since they merely snap on and off. After the trim was removed, the hull cutout was easily visible and measureable, revealing my first challenge: the hull cutout thickness (40-50mm) was slightly more than recommended in the installation instructions. This was somewhat of an issue since the included stainless steel metric screws used to attach each portlight were too short, and replacements of the proper length weren’t easily available at the local hardware stores. The screws couldn’t be too long, either, because they can’t contact the outer flange of the frame without stripping the inner flange screw holes. Additionally, the plastic trim might not quite be long enough.

Measuring the screws used to attach the old portlights, which didn’t seem to use metric threads, led me to order a bunch of 40, 45, and 50mm screws from McMaster-Carr. Since McMaster ships from several locations in the US, including Chicago, I received them within 48 hours of my order.

I removed and replaced each portlight before moving to the next portlight so if I encountered obstacles along the way I wouldn’t have too many holes in the boat. Since there’s no cure time with my chosen bedding sealant, I could replace one portlight in the morning, then go for a sail in the afternoon, spreading the project over a few days (some I did in the boatyard).

Prior to removing each portlight, I test fit each new portlight over the old to see how reasonable the fit would be… the New Standard Portlights have a slightly different curve in each corner than the Old Standard, though it was always a good fit on Priorities.

Removing the old portlights were really the only other minor challenge. Catalina installed them with a sealant that has some adhesive properties (maybe 3M 4200), so I had to carefully use a hammer and putty knife to break the seal after removing the screws. Each portlight took 30-45 minutes to remove because of this.

Hull cutout after old portlight removed
Hull cutout after old portlight removed
Portlight removed
The cabintop is fairly thick on Priorities, as seen here. This thickness is why I had to order longer screws. A hard foam fills the gap between the fiberglass deck/cabintop and the interior fiberglass headliner.

In preparation for the new portlight, I spent a little time making sure the gelcoat around the opening was clean and smooth. It doesn’t need to be perfect, but removing silicone or other old caulk is important for getting a good, watertight seal when using any bedding compound.

As a sealant, or bedding, for the new portlights I used Bed It Butyl Tape by Compass Marine. Compass Marine is owned by Practical Sailor contributor Rod Collins, who also regularly contributes his expert advice as “MaineSail” on various boating web forums like Sailboat Owners.com. I’ve used his butyl tape for bedding lots of deck hardware and it’s been excellent… it works very similar to plumber’s putty, but in tape form and a little bit stickier.

Adding Butyl Tape to portlight
Butyl Tape was used as bedding compound. I used a tape layer, then a hand rolled beaded layer to cover any hull curvature.

After carefully squishing each new portlight in place, I gradually tightened the mounting screws in back. I tightened in a sequence similar to tightening a cylinder head, working my way from screws in the center and out to screws in the sides of the frame. Since there’s only about 7 or 8mm of space between the inner and outer flanges of the frame, and the screws can strip if they are screwed in too deeply, I would start with using screws that were just barely long enough to get a few threads in the frame. After a few rounds of gradually tightening each of the 12-16 screws, which also squished the bedding compound, I would replace some of the screws with slightly shorter screws one by one, thus allowing me to gently bring the screws to final torque without hitting the other flange of the outer frame. Final torque should only be 25 in-lb., which isn’t super tight.

New portlight installed, but with no trim
New portlight installed, but with no trim. 16 screws!

Approaching final torque, I tested the operation of the portlight by opening and closing it a few times. The new portlights are built so solidly I never really got worried about it binding when opening or closing.

Newly installed portlight
Testing opening of the newly installed portlight

A cool thing about using butyl tape is that it never cures or dries. However, it does slowly “ooze,” so a day after installation I retightened the screws to final torque, then carefully trimmed the excess butyl tape away. When trimming the butyl tape, it’s important NOT to pull any more material out from under the frame… I used a sharp knife to cut the excess.

Portlight with butyl tape showing
Here the butyl tape has squished slightly out from under the frame. I trimmed this excess about a day after installation.

I tested watertightness with a hose, as well as after several rainstorms, and never had any issues.

After testing for watertightness, I installed the new trim piece. The plastic trim simply snaps in place on the inner frame after trimming its depth to fit. Since all of my portlights were in thick parts of the hull, mine required no trimming at all. A small, nearly invisible space exists between the trim and the inner flange of the outer frame, and I may fill that gap with a white tape to prevent water from getting trapped between the trim and the hull… if I ever get around to it.

Portlight with small gap between trim and outer frame.
There’s a small gap between the plastic trim and the outer frame, though it isn’t that big of a deal.

In the end, each portlight took about two and a half hours from start to finish, not including time to measure or read the instructions. It actually was pretty easy, too, and now we have clean, leak free, opening portlights in both our heads!

Newly installed portlight.

Leave a Reply