View Full Version : drilling thru-hulls below the rubrail

05-04-2007, 09:28 AM
I'm about to drill 4 holes just below the rubrail for ballast empty. My question is, is there a way to make a clean hole through the carpet on the inside of the hole? I was thinking maybe hold a block of wood up on the inside of the boat while drilling from the outside. Any ideas?

I don't need advice on protecting the gelcoat, etc, that is pretty well documented in other forums.

05-04-2007, 09:43 AM
Erik, I just did the same thing 2 weeks ago. After I got the exact placement of the hole, I used the plastic nut on the thru-hull as a template and drew a circle on the carpet with a Sharpie; if you have dark carpet use chalk.

Then I scored the carpet with a utility knife and pulled the carpet circle out before I drilled the hole. The edges were a little ragged but that is covered up by the plastic nut.

05-04-2007, 09:43 AM
Depending on the size of hole you are talking. I would use a leather hole punch with wood behind the carpet. Have never had any luck usinr a hole saw with carpet. :noface:

05-04-2007, 09:52 AM
Peel the carpet back, drill a pilot hole in the fiberglass, make the hole you need FROM THE OUTSIDE and cut an X in the carpet over the hole or use the hole as a template to cut the hole with the tip of the blade.

That's what I would do. Also, ease the outside of the hole, countersink it or use a small dowel with sandpaper, so the gelcoat doesn't crack.

05-04-2007, 12:15 PM
I'm about to drill 4 holes just below the rubrail for ballast empty.

Erik, 4 holes? why not just 3? You are using 3 Tsunami's to fill, right?

05-04-2007, 02:03 PM
I highly recommend a RotoZip if you have one or can borrow one. I used that to install my pull up cleats and it made my life so much easier. The cuts are very clean and it doesn't leave any jagged edges. Once you finish your holes, make sure you use a fine grit sandpaper to smooth out the hole to prevent cracking later.

05-07-2007, 10:45 AM
I've already drilled 2 thru-hulls under the boat that turned out very clean, so I'll probably stick to the hole saw.

Did I say 4 holes? I meant 5. I want a seperated thru-hull for each empty pump. 2 empty pumps on the integrated bow sac, one on the center sac, and 1 each on the rear bags.

Rich, I'm using one fill line on the integrated bow sac because it will only get 300 lbs or so, two empty lines on it to get all the water out. My manifold will feed the two rear bags and the integrated bow sac. For the middle bag I "borrowed" the center drain hole, which was a perfect fit for an Attwood 750 aerator pump.

05-07-2007, 02:01 PM
Hi etakk7,

sounds like a SWEET ballast system your making. Be sure to take LOTS of pics :)

I may know someone who's going to do the same thing soon:D