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Sizing Your Porthole

How to determine your portlight size

Step 1: You will need to know the dimensions and thickness of your cutout.

If you haven’t removed your existing portlights, make note of their glass size, overall dimensions and estimate the cabin side thickness.

You may consult our list of Portlights by Boat Manufacturer to see what other owners have purchased from us, but this does not replace the need for you to make your own measurements.

image of portlight glass size vs. overall size

Step 2: Look at our portlight dimensions to find a port that matches the overall size or is slightly larger.

Our ports are named by their nomial glass size, so consult our dimensions drawings on our portlight product pages for overall and other dimensions. For example, a common plastic port has an overall dimension of 7 3/4″ x 14 3/4″. Our 5×12 port has an overall size of 8″ x 15″, which will hide the footprint left by the existing portlight.

When you pull your old port, you may find that cutouts vary considerably. You can remove cabin side material where necessary and fill gaps with caulk when the cut out is a bit oversize. Remember, our ports bolt through so a variance in cut out size will not matter to the structural integrity of the installation. We recommend you review our portlight installation guides.

Step 3: Determine what size spigot to order (Standard or Extended).

We stock ports with standard 1-1/2″ and extended 2″ spigots. The amount of spigot that will protrude past the finishing ring is proportional to the wall thickness the spigot is passing through. For example, if you have a 1″ cabin side, the spigot on a standard portlight will not protrude more than 1/2″ past the finishing ring. The maximum cabin side thickness a standard port can be mounted on is 1-1/2″. We can special order spigot lengths – ask us for a quote

Note that our TriMatrix ports have their own cabin side requirements – please see our online TriMatrix installation guide for more details. Please see our downloadable Care & Maintenace Tips.

image of spigot sizing information

Step 4: Place an order or request a quote.

You can contact us by email, phone or fax. For a list of sizes and prices for our portlights, go to our online catalog or download a price list here. You may see our ports in person, by visiting our display at many nation-wide boatshows. Or check out our customer reviews page.

How to measure your cabin-side thickness.

How to measure the thickness of the cabin side without removing the existing port window

Watch our video here, or read through the step by step instructions below.

Step 1: Measure Inside to Outside

Measure from the very outside to the very inside of your port window, including the outside spigot and inside flange.

The port to the right measures 2-½”.

Step 2: Measure Inside

Measure from the inner cabin side to the edge of the flange.

Port shown measures ¾”.

Step 3: Measure Outside Spigot and Finishing Ring

Measure from the outer-cabin side to the edge of the spigot.

Port shown measures ½”.

Step 4: Calculate Cabin Side Thickness

Add the depth of the port on the inner cabin side (Step 2) and the depth of the port on the outer cabin side (Step 3).

The port shown here is

½” + ¾” = 1-¼”.

Now, subtract from this from the overall port thickness (Step 1) to derive cabin side thickness. The port shown here has a cabin side thickness of

2-½”– 1-¼” = 1-¼”.