This article tells you what you need to know on portholes:
Depending on your budget or taste you can choose for second hand portholes or buy new ones. You can find second hand portholes on a scrapyard or by a dealer. New portholes can be found on several locations.
There are different type of portholes available
On the Watergeus, I've used second hand portholes from a scrapped dredger end from two scrapped barges. The process is being showed in pictures.
Placing portholes with a tube
This section is illustrated and based on my experience aboard my boat, the Watergeus. I bought these portholes from a friend who salvaged them from a dredger.
Just bought the portholes, need to clean them first
Making the holes with a graining disk. Burning will put to much heat in the metal and bend it.
The holes are made, starting to look nicer
The tubes are in position and welded
The glass has been placed in the portholes.
Everything received a nice coat of paint
Placing portholes without a tube
There is also the option of putting portholes in the den straight away without the use of a tube. Therefore, only a hole needs to be grained and a few holes drilled for the bolts.
Drilling the holes for the portholes
Closed & open portholes
Closed portholes are cheaper, but they can't be opened, what is not as nice. You can't have fresh air through them. What is often done is a combination of open and closed portholes.
One big porthole that can open and several closed one's
Portholes seen from the inside
Portholes boxed in aboard the house boat museum Hendrika Maria in Amsterdam