Forward fish box drain (Update)

CHANCE1234 · #1 12-13-2014, 09:25 AM

1972 20 SF.

The previous owner glassed over both the inside and outside holes of my forward fish box. I can't even tell where the original hole was on the outside of the hull. What is the easiest way to drill the hole in the original location. I would think the angle needs to be perfect so the flange of the tube lines up correctly both inside and out. The preferred method to drill this would be from the outside I think but I don't know the exact location to get the hole to come out where it should on the inside. Anyone ever done this or have any ideas? Thanks.

wattaway2 · #2 12-13-2014, 01:06 PM

Others will likely have a better idea but my thoughts go to going from the center of the drain well assuming it's still there and doing a very small pilot drill bit out ward . You can the take a PC of coat hanger wire and run it thru to check your alignment. The inside box and the outside should be very close in there alignment already but you could check you hole and adjust it from the outside within reason

CHANCE1234 · #3 12-13-2014, 02:58 PM

That was what I was thinking too. Any idea how thick that area is? Is it right against the hull or will it be inner liner followed by a void than the hull? Thanks

CHANCE1234 · #4 12-13-2014, 11:04 PM

So I drilled a small hole from the inside after removing the hack job patch that covered it. The old hole looks to be filled with just resin. Does anyone know if there was a wood block under there like the original thru deck scuppers? Also can someone measure the inside diameter of this drain for me so I can drill the right size hole? Thank you.

oldfielder · #5 12-14-2014, 10:43 AM

When I removed that drain there was a big glop of "potter putty" between the liner and hull and there is definitely a void in there. I think it's a pretty notorious leaking spot. I replaced it with a more substantial thru-hull.

CHANCE1234 · #6 12-14-2014, 11:01 AM

I was thinking of drilling it out a little bigger than a fiberglass tube from McMaster Carr. Then insert the fiberglass tube and ensure it is flush with the bottom of the hull by placing a board and support under it to hold it in place then inject west system with a syringe around the entire tube from the inside to bond it in place. Remove bottom support, insert plug and go. Any issues with this plan

oldfielder · #7 12-14-2014, 11:15 AM

I wanted a mechanical bond in addition to sealant/adhesive so I used a low profile threaded thru-hull cut down to size. It protruded a bit but it's not really running surface right there anyway.
The only worry I would have with what you want to do is not having the epoxy just run away when you inject it. Also, you have to figure you get a lot of vibrational forces right there when blasting through chop so you want a substantial bond.

Bushwacker · #8 12-14-2014, 01:02 PM

Quote:

Originally Posted by CHANCE1234

I was thinking of drilling it out a little bigger than a fiberglass tube from McMaster Carr. Then insert the fiberglass tube and ensure it is flush with the bottom of the hull by placing a board and support under it to hold it in place then inject west system with a syringe around the entire tube from the inside to bond it in place. Remove bottom support, insert plug and go. Any issues with this plan

Chance, I had a similar problem with the OEM scupper tubes, where the wood block surrounding one of them was rotted pretty good. I carved out the rotted wood as best I could and then basically filled the entire hole with epoxy and redrilled it like you're planning. Instead of using straight epoxy which will just run all over the place, I'd thicken it to about the consistency of peanut butter to keep it from running and then use an empty caulk tube (many FG suppliers carry them) to force thick epoxy into the gap.

Here's the text of a post I made on the subject that might give you some more ideas: 06-04-2007, 12:13 AM
Epoxy fill of scupper holes using PVC core/pilot hole worked out well - mismatch between original hole & drilled hole at bottom was about 1/32", easily filled with 5200. Would have probably been better if I had used a flat wood drill bit with pilot feature instead of conventional bit which tended to walk.

Epoxy Fill: You will probably discover that the wood block is no longer sealed to the hull, so if you try filling it with plain epoxy as I did, it just runs out at the bottom. Next try with epoxy thickened to about apple sauce consistency worked well. I used MAS slow cure hardener & chilled it & resin in fridge first; otherwise it wants to kick off pretty fast once you pour it in caulk tube! Ended up using 3 caulk tubes, but wasted one due to sealing problem mentioned above.

Brass Tube Installation: (Ordered 1" ID x 6" long brass tubes from Boat Owners Warehouse, about $6 ea., got them overnight) The hole came out about 1/16" oversize due to drill walk, so filled it with 5200 as I slid tube in from top. Installed drain plug in top of tube first for leverage. Need to flare bottom of tube right away to keep 5200 from running out bottom because it's pretty slow to cure. Used a threaded rod, with nuts, washers and a 1/2" drive socket to get the flare started.

Results: After letting the 5200 cure for about 5 days, took the boat out for about 6 hrs, 4 of which was at anchor, bilge pump OFF for entire time. Pulled boat out, pulled bilge plug - it was dry, didn't leak a drop!

Here's a slideshow with some pics I took of process. I like the idea of using a threaded thru hull for your application, so you'll have some mechanical compression keeping it together to fight vibration and relative motion between hull and inner liner/box that might loosen or crack the bond with a tube just stuck in with epoxy. In your case the trick will be to get a complete ring of thickened epoxy around the hole in the gap between box and hull. You don't have a 4-5" long hole to fill like I did, so maybe you could just use a putty knife or chisel blade in an exacto knife to fill the gap, or put some tape on inside of hole and drill some small holes around circumference of big hole and use caulk gun to inject thick epoxy thru them.

CHANCE1234 · #9 12-14-2014, 01:53 PM

Oldfielder what did you use for a low profile threaded thru hull? Thank you

oldfielder · #10 12-14-2014, 02:06 PM

Pretty sure it was a 3/4 bronze mushroom. I dry fit it, measured and marked the threads and then cut it down with a hacksaw. Two man job to install. One guy holding the nut on the inside and one guy turning it with a step wrench on the outside. Pretty sure I sealed it with 5200. If I were you I would drill the hole and then fill the void around the hole with peanut butter. Let that set up and then use above method. This way when you go to install thru hull you won't compress the space.
http://www.perko.com/catalog/underwa...use_with_pipe/