jimh wrote:When the wall thickness of the tubing increases, the effectiveness of the drain is reduced. The original drains use a rather thin-wall brass tubing, so the effective size of the drain is nearly the same as the hole size.
What is the inside diameter of the fiberglass tubes you are using for drains?
The flow is not reduced if you replace the brass tubes with fiberglass tubes with the same ID. You have to increase the size of the factory holes but that is an incredibly easy and inexpensive process. In fact, I had already purchased the brass tubing, O rings and flare tools before I made the decision to switch to fiberglass. Switching to fiberglass tubes are way less expensive (you don't need to purchase flange tools) and will never rot or corrode.
To increase the size of the holes purchase this $7.99 drum sanding kit from Harbor Freight
https://www.harborfreight.com/sanding-d ... 60741.html . Insert the largest drum that will fit in your hole and slowly sand the hole larger. When you get the tube to slide in, on each side you know you have the correct size. Once you have cut the foam out to the new diameter, clean everything well with acetone and the hull is ready.
Then sand the outside of the Fiberglass tube, clean it with acetone and epoxy it in place. I used white Marine Tex because it is so easy to use.
I like Marine Tex because if you catch it at the correct dry time you can use water and a tongue depressor to smooth it out instead of waiting until hard to sand. You can literally use water and your finger to smooth it out to a shiny finish. You get good at it to the point sand paper is not necessary.
If you are restoring your boat and will be sanding for paint or gelcoat, you can leave the tubes slightly long and sand them down to a completely smooth finish.
[A new topic about how to modify the way water drains on a 22-foot hull is now moved to its own thread--Moderator]