Beneteau First 235 Home
Let there be Light...and Breeze ! Opening Cockpit Portlight
By Mike Hayden & Windependent

The aft quarter berth on the First 235 offers reasonable accommodations for one or two people depending on size. But those sleeping quarters get stuffy and crowded fast because of the lack of ventilation in the stock boat.  You could replace the 8" round fixed port with one that opens - but there is an awful lot of water right there.  I decided to add an opening portlight into the cockpit.  It adds ventilation and as a bonus lets in even more light.


• 1 Lewmar Size 0 Standard Port Light, # 393020500 Opening Smoke Grey
This portlight is rated for use on the exterior hull above the waterline, and stays water tight even at 5 PSI.  This kit includes a bug screen, too.
• Sealant/Caulking 3M 4200 (white)
• 1 piece 14" x 8" x 1/8 masonite
• Masking tape
• Kraft paper
• Paper towels

Tools Needed:

• Electric Jigsaw (with a smallish body - see text)
• Electric Drill
• Coarse File
• Phillips screwdriver
• Mineral spirits


The tough part of this whole thing is not the portlight work but rather the mental decision associated with making a GIANT "forever" hole in your pretty boat.  I do not even like drilling a 1/8 through my deck, so this took some guts.  No, make that LOTS of guts.

Installation of the portlight itself is easy and only takes a couple hours.  In the following picture clockwise from the upper right:  The portlight (fits in from the outside of the boat), the backing plate (its on from inside), and the trim panel (snaps in place when you are totally finished).



Start by making a template out of Kraft paper.  The Lewmar kit does not come with one.  The template opening should be 156mm x 303mm.  The corners have 52mm radius.

Consider the location of your portlight carefully.  There is not a lot of flat real estate in the cockpit wall.  Near the floor of the cockpit, it is rounded.  Near the seat the vertical surface slopes under the handrails.  The Lewmar Size 0 is about the biggest you can fit height-wise. If you want to install something larger, measure very carefully before you order.  The portlight MUST mount perfectly flat or you won't be able to make it watertight.  I decided to place mine enough foreword so it wasn't behind the gas tank I normally keep in the stern.  The portlight can go farther aft if you like. Tape the template to the cockpit wall, making sure it is parallel to the hand rails.  Then trace the opening with a soft pencil and remove the template (save it for a later step).



Inside the quarter berth, pull the carpet headliner away from the area where you will be cutting the hole.  Go back outside.

If you are sure you want to do this, drill a starting hole big enough to allow your jig saw blade.



Sailor, you are now definitely committed, like it or not.

Put a few layers of masking tape around the opening for the jig saw to ride on so the surface doesn't get messed up.  Saw out the opening with a jigsaw.  I found the gel coat did not crack or shatter, but rather cuts with a nice clean line, leaving a lots better edge that I thought it would. But cutting fiberglass is brutal to the saw blade.  By the time I was done the opening the blade was toast (see just above the baseplate where all the cutting took place - Look, Ma. No teeth!):



The hole turned out well. There was just enough clearance to negotiate the jig saw all the way around.  If your jigsaw is too big you will have to go to Plan B (and that's up to you!).  Make sure the portlight fits in and lays perfectly flush against the cockpit wall.  File the hole a little if needed.

Inside the boat, cut the headliner out to the size of the fiberglass opening.  Then fold or pin it well out of the way.



The portlight REQUIRES a minimum wall thickness of 6mm in order to clamp tight, and you cannot cheat here.  The First 235 wall thickness in this area is not enough being only 5 1/2 mm on my boat.  Use the template and trace the opening onto the masonite. Draw a second line all around the first line about 1" farther out.  Cut it out, which will result in a big, oval shaped 1/8" thick masonite washer.



Dry fit the portlight and hold it in the hole with some masking tape.  From the inside slide the wooden washer over it.  Make sure that the portlight goes through the masonite and that the masonite is pressed 100% flush against the inside of the cockpit wall.  This makes the wall of the cockpit 1/8"  thicker, and is just what you need.  Place the metal Backing Plate over the inside of the portlight making certain the proper side of it faces inboard (it's marked with a sticker).

The portlight comes with a dozen M5 x 20 screws.  They are way too long for our thin walls.  Cut them to a length of 12 mm from the underside of the head to the end of the screw.  Use a hacksaw.  Cut just one initially and test fit it.  They are screwed in from the inside of the boat.  If they are too short they won't catch the threads of the portlight.  If they are too long they will physically damage the aluminum trim ring around the outside of the portlight in the cockpit.  Cinch down the test screw and try to wobble the portlight athwartship. It should have zero play and feel rock solid.  If the screw length is OK, cut the rest of the screws to the same length.

Remove the portlight from the hull.  Run a 1/4" bead of 3M 4200 (or a good marine grade silicon) all around outer inside edge of the portlight.  More is better than too little. Push the portlight into the opening, press it firmly and make it flush.  Sealant should ooze out around the edges. If not, pull it out and add more sealant.  Let the oozage just sit there.  It will take a couple of hours to cure, you have plenty of time to clean it up after the next steps.

From inside the boat, run a 1/4" bead of sealant all around the portlight making a gap-filling filet between the hull and the portlight body. Don't skimp. Then press the masonite washer over the portlight, thus squashing the sealant in place.  Place the correctly oriented Backing Plate into position and attach it loosely with the 12 screws.  Once all screws are started, tighten opposite screws (like you're putting on a spare tire) until all are good and tight. Your goal is a backing plate-masonite-hull sealant sandwich that is flush, solid, waterproof and immovable. The slightest movement means trouble. You have to take the time to correct it.  It should feel absolutely solid.  Stop tightening the screws when you think they have 1/8 turn left.  You'll come back TOMORROW and take that last 1/8 turn after the sealant has cured.

Here's how the inside should look (my masonite is white on one side and brown on the other - here you see the white side)



Out in the cockpit, check to make sure the portlight is absolutely flush to the cockpit wall.  Using your finger tip, filet the oozed sealant all the way around.  Take care not to get sealant on the acrylic window.  Clean up the aluminum trim and fiberglass with a paper towel moistened with mineral spirits.

Allow 24 hours for the sealant to set up.  Then take the last 1/8 turn on the screws. Take the plastic trim panel and cut it's spigot length down to the proper size so it can snap into position over the inside of the portlight.  This is easy and you can use scissors or a snipper.  Final trim the headliner so it butts up against the edge of the aluminum backing plate. Re-glue the headliner.  Snap the trim panel in place (it will also hold the edges of the headliner captive).

Here's the nice result:



Next, I need to do something about that pathetic weathered teak!

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