Introduction: Install an Inspection Port in a Sunfish Sailboat

So, you want to install an inspection port (also called a deck plate) in your Sunfish deck? They can help you dry out the hull and also make interior repairs such as fixing loose backing blocks for your halyard cleat or other hardware. Sometimes there aren't backing blocks if they fell off or the previous owner added hardware without doing a proper backing. Without backing, the screws could pull out of the fiberglass and damage your hull (and lead to disaster on the water!). It also gives you access to properly install a hiking strap if your sunfish is too old to have one already. These instructions show installation of the port fore of the footwell, but if you are upgrading your very old sunfish from the old rudder style to the new one, you can add a port near the transom to help with that upgrade. On one of these boats, we added a total of 3 ports because it needed repairs in several places!

I have helped a few friends put ports in their sunfish/minifish and we took pictures along the way to help show you what to do. This instructable has photos from 3 different boats to show you how it might vary, but don't worry that the boat color or port locations change a little between steps, we did all of them the same way.


  • Sunfish or Minifish sailboat
  • drill and bit that is as wide as your jigsaw blade
  • jigsaw
  • blue tape
  • 100% silicone sealer (clear)
  • inspection port (I used Sea Dog 337150-1 Screw Out Deck Plate, 5-7/16" / White")
  • 6 small stainless steel screws

Step 1: Prepare the Sunfish and Choose Location for Hole

On a sunfish, most people seem to prefer putting the port centered in front of the daggerboard slot and behind the coaming. The advantage is that you can access the front of the footwell if you need to add backing to screws holding in a hiking strap, and you can also reach the hardware for the halyard near the mast step tube. This also lets you inspect the daggerboard slot and mast tube for any damage, and repair it from the inside if needed.

Step 2: Tape the Hole Location and Trace the Outline

Once you choose the location, put down tape to protect your deck from the jigsaw. It also helps minimize chipping of the gelcoat.

Once you have it taped, use the deck plate itself to trace out the hole. Turn it over and lay it on the tape so that you have the threads facing up. Use a thick marker to trace the outline so you can easily see it while using the jigsaw.

Step 3: Drill a Pilot Hole for the Jigsaw Blade

Next, you need to drill a pilot hole so you can insert the jigsaw blade. Choose a drill bit that is the same size as your jigsaw blade, and then drill a hole on the INSIDE of the circle that you drew in the previous step.

Step 4: Use the Jigsaw to Cut Out the Opening

Next, insert your jigsaw blade into the hole before you turn it on. Go slowly and cut carefully on the circle. It doesn't have to be perfect, you will have the flange on the outer ring of the deck place that will cover any small errors in your cutting. If you go too small, though, the ring won't fit in the opening without some extra trimming later. Once the hole is cut all the way around, remove the fiberglass circle. You can save this in case you need to make any hull patches in the future.

It can be a good idea to wear a face mask during this step to avoid breathing in any fiberglass dust!

Step 5: Remove the Tape and Clean Up the Edges

Now you can remove the rest of the tape and lightly sand the edge if needed. Clean up any pieces of interior foam block that might overlap your hole.

Step 6: Test Fit the Port Ring to Make Sure It Fits

Put the ring in the hole to see if any trimming is needed. Don't use sealer yet!

Step 7: Look Inside the Hole and Check for Damage or Loose Blocks

Now that you have an opening in your sunfish, use a flashlight or your phone camera to take some pictures inside the hull. Look carefully at the mast tube and daggerboard slot to check for damage. You can also do this when it's in shallow water to see if these locations have any leaks.

Next, look up at the underside of the deck and check the backing blocks near your halyard hardware. Depending on the year you'll have a turning block and cleat, or maybe a fairlead and cleat. Both of these should have backing blocks! Note in one of these photos that there are screws coming through the fiberglass without a backing block. These screw held in the turning blocks for the fairlead, and if the halyard was pulled too hard these might have come out. We added a backing by removing the screws and then epoxying a small wood block there before reinstalling the screws.

Next, notice in the picture that the backing block for the cleat was loose and fell off after we removed the screws for the cleat. This needed to be epoxied back to the hull after the wood block was removed and allowed to dry out. These steps are very important to protect your hull, and also to avoid disaster if they pull out during stress while out on the water.

Step 8: Add Silicone Sealer to the Ring and Put It in the Hole

Now that you've done your repairs, it's time to add a continuous strip of pure silicone sealer around the outer ring and then insert it gently into the hole. Be careful with the silicone and don't get it on your clothes. Wearing disposable gloves can help too- it doesn't wash up very easily. Press it down lightly so that the silicone oozes out a little, but you want some to stay in and form a gasket all the way around so don't press down so hard that it all comes out! If you look closely at the photo you'll see a little bit oozing up in each screw hole. This is fine, it will form a seal for the screws. Make sure to press evenly all around so that you see a seal formed around the entire circumference of the ring. Let this cure overnight.

Step 9: The Next Day, Drill Pilot Holes and Add Stainless Screws to the Ring

Once your silicone has cured, you want to take a small drill bit and drill pilot holes in the fiberglass through the holes in the deck plate outer ring. Don't make them too large! Use a drill bit that is much smaller than your screws. Screw in the screws by hand, being careful not to tighten too much. The silicone will do a good job as an adhesive holding in the plate, these are just to give it extra strength but do not need to be so tight that you risk stripping the fiberglass.

Make sure you use stainless steel screws! You don't want them to rust.

Once the screws are in, screw in the deck plate by hand.

You're done! Now you have an easy way to do repairs inside your sunfish, and also check for leaks or easily dry it out. I usually leave the cover open in warm weather to let the hull air out.

Step 10: Repair Any Hull Cracks With Fiberglass

Once last step - check the bottom of your hull for any stress cracks that can leak. In this photo we show 2 spots where there were cracks in the hull where water leaked in while sailing.

First we sanded down the area around the cracks to get rid of dirt and loose fiberglass. Then we used a Bondo "stage 2" fiberglass repair kit (fiberglass cloth along with a 2-part resin that you mix and brush on the cloth). It can be found online and in walmart or auto stores for around $10-15. Cut the cloth a little larger than the area needing repair. Brush resin on the cracked area, then add cloth and use the brush to pat down the cloth and remove any air bubbles. Brush on more resin, overlapping the cloth by about 1/2". Add another layer of cloth and repeat. We used 3 layers of cloth for these cracks, and when it cured we lightly sanded the area and then used Rustoleum Topside white paint. It's hard to see the repair!

We didn't get more pictures of this step - sorry!