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How to install an inspection port.

Step 1: Why and Where???

An inspection port is a removable deck plate that will allow you to access the inside of your hull. Even in a new boat like a Sunfish I typically install one right away so that I can keep the hull properly dried inside. Other reasons include access to the inside to allow for repairs or ports with "cat" bags can be installed to allow for storage. The job is not very complicated and can be accomplished in about 1/2 hour. The ports are available most commonly in 4,5 and 6" sizes. Some come with a "cat" bag that fits inside and allows for secure storage of small items such as keys or a can of Coke.

Where to put the port in will be determined by several factors: access to repair something specific; general maintenance; structural elements that should not have holes cut in them.

You will need: Inspection Port, Marine Caulk, Screws or rivets, Drill, Saber or Key hole saw, Center Punch, Compass Screwdriver and some tape

Step 2: Preparing to Cut the Hole.

Nobody blithely cuts a hole in their boat. Especially not a newer boat so choose the point where you want the port carefully.

Start by taking a center punch and making a small depression at the center of the circle. (Fig. 1) This will make a good centering point for your compass.

Fig. 1 Fig. 2

Using the compass draw a circle with a diameter corresponding to the port's manufacturers recommendations. (Fig. 2)

Using a drill with a 1/4 - 3/8" bit, drill a hole just inside the perimeter you have drawn. (Fig. 3)

Fig. 3

Step 3: Cutting the Hole

If you are using a Saber Saw use tape on the underside of the metal guide so that you won't scratch the fiber glass.

You will want to use a metal cutting blade to cut the hole in the glass. It may take 2 or 3 blades to complete the job. (You would be amazed at how fast the fiberglass will abrade the saw teeth.) Also, the finer teeth will give you a smoother cut. Place the blade of the saw in though the hole and carefully cut along the line you drew with your compass. (Fig. 4) It is often easier to work your way from both sides of your starter hole than to try and cut all the way around in one sweep.

Fig. 4

When you are finished cutting, dry fit the port in the opening to make sure it fits. Readjust the hole as necessary.

Step 4: Mounting the Port.

Start by putting a thick bead of caulk around the perimeter of the hole. (Fig. 5)


Insert the port into the hole and turn it 1/4 turn to make sure it is properly seated in the bed of caulk. (Fig. 6)

Fig. 6

You will finish the job by fastening the port in place with either screws or rivets. Drill only one hole at a time. Then put a dab of caulk in the hole and finish it off with a rivet or screw. Then do the hole on the opposite side of the rim the same way. By doing the holes one at a time you will avoid mislocating holes. By working on opposite screws you will avoid inadvertently distorting the rim of the port and ruining it's water tight integrity.